fix: some improvements to GET chunk writing (#2853)

* fix: some improvements to GET chunk writing
 - ensure levelChunk is loaded before giving to copy GET - this is not necessarily guaranteed to be nonnull if two edits overlap. Whilst not advised, such an easy failure should not occur when two edits collide

* Prevent writing chunk sections when FAWE is also sending packets for a chunk and vice versa
- alter IntPair hashcode to be more often unique
- Utilise ConcurrentHashMap for free synchronisation

* Minor comment changes

* Use one-per-world-instance FaweBukkitWorld to store world chunk map

worldedit-bukkit/adapters/adapter-1_20_2/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R2/PaperweightGetBlocks.java

@@ -7,6 +7,7 @@ import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.configuration.Settings;
 import com.fastasyncworldedit.core.extent.processor.heightmap.HeightMapType;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.nbt.FaweCompoundTag;
 import com.fastasyncworldedit.core.queue.IChunkGet;
 import com.fastasyncworldedit.core.queue.IChunkSet;
@@ -106,6 +107,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     private final ServerLevel serverLevel;
     private final int chunkX;
     private final int chunkZ;
+    private final IntPair chunkPos;
     private final int minHeight;
     private final int maxHeight;
     private final int minSectionPosition;
@@ -140,6 +142,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
         this.blockLight = new DataLayer[getSectionCount()];
         this.biomeRegistry = serverLevel.registryAccess().registryOrThrow(BIOME);
         this.biomeHolderIdMap = biomeRegistry.asHolderIdMap();
+        this.chunkPos = new IntPair(chunkX, chunkZ);
     }
 
     public int getChunkX() {
@@ -425,7 +428,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             throw new IllegalStateException("Attempted to call chunk GET but chunk was not call-locked.");
         }
         forceLoadSections = false;
-        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(levelChunk) : null;
+        LevelChunk nmsChunk = ensureLoaded(serverLevel, chunkX, chunkZ);
+        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(nmsChunk) : null;
         if (createCopy) {
             if (copies.containsKey(copyKey)) {
                 throw new IllegalStateException("Copy key already used.");
@@ -433,9 +437,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             copies.put(copyKey, copy);
         }
         try {
-            ServerLevel nmsWorld = serverLevel;
-            LevelChunk nmsChunk = ensureLoaded(nmsWorld, chunkX, chunkZ);
-
             // Remove existing tiles. Create a copy so that we can remove blocks
             Map<BlockPos, BlockEntity> chunkTiles = new HashMap<>(nmsChunk.getBlockEntities());
             List<BlockEntity> beacons = null;
@@ -507,6 +508,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                             biomeData
                                     );
                                     if (PaperweightPlatformAdapter.setSectionAtomic(
+                                            serverLevel.getWorld().getName(),
+                                            chunkPos,
                                             levelChunkSections,
                                             null,
                                             newSection,
@@ -584,6 +587,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeData
                             );
                             if (PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
                                     levelChunkSections,
                                     null,
                                     newSection,
@@ -649,6 +654,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeData != null ? biomeData : (PalettedContainer<Holder<Biome>>) existingSection.getBiomes()
                             );
                             if (!PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
                                     levelChunkSections,
                                     existingSection,
                                     newSection,
@@ -722,7 +729,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                         }
                         if (Settings.settings().EXPERIMENTAL.REMOVE_ENTITY_FROM_WORLD_ON_CHUNK_FAIL) {
                             for (UUID uuid : entityRemoves) {
-                                Entity entity = nmsWorld.getEntities().get(uuid);
+                                Entity entity = serverLevel.getEntities().get(uuid);
                                 if (entity != null) {
                                     removeEntity(entity);
                                 }
@@ -761,7 +768,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
 
                             EntityType<?> type = EntityType.byString(id).orElse(null);
                             if (type != null) {
-                                Entity entity = type.create(nmsWorld);
+                                Entity entity = type.create(serverLevel);
                                 if (entity != null) {
                                     final CompoundTag tag = (CompoundTag) adapter.fromNativeLin(linTag);
                                     for (final String name : Constants.NO_COPY_ENTITY_NBT_FIELDS) {
@@ -770,11 +777,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     entity.load(tag);
                                     entity.absMoveTo(x, y, z, yaw, pitch);
                                     entity.setUUID(NbtUtils.uuid(nativeTag));
-                                    if (!nmsWorld.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
+                                    if (!serverLevel.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
                                         LOGGER.warn(
                                                 "Error creating entity of type `{}` in world `{}` at location `{},{},{}`",
                                                 id,
-                                                nmsWorld.getWorld().getName(),
+                                                serverLevel.getWorld().getName(),
                                                 x,
                                                 y,
                                                 z
@@ -804,11 +811,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                             final int z = blockHash.z() + bz;
                             final BlockPos pos = new BlockPos(x, y, z);
 
-                            synchronized (nmsWorld) {
+                            synchronized (serverLevel) {
-                                BlockEntity tileEntity = nmsWorld.getBlockEntity(pos);
+                                BlockEntity tileEntity = serverLevel.getBlockEntity(pos);
                                 if (tileEntity == null || tileEntity.isRemoved()) {
-                                    nmsWorld.removeBlockEntity(pos);
+                                    serverLevel.removeBlockEntity(pos);
-                                    tileEntity = nmsWorld.getBlockEntity(pos);
+                                    tileEntity = serverLevel.getBlockEntity(pos);
                                 }
                                 if (tileEntity != null) {
                                     final CompoundTag tag = (CompoundTag) adapter.fromNativeLin(nativeTag.linTag());
@@ -827,7 +834,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                     callback = null;
                 } else {
                     int finalMask = bitMask != 0 ? bitMask : lightUpdate ? set.getBitMask() : 0;
-                    boolean finalLightUpdate = lightUpdate;
                     callback = () -> {
                         // Set Modified
                         nmsChunk.setLightCorrect(true); // Set Modified
@@ -933,7 +939,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     @Override
     public void send() {
         synchronized (sendLock) {
-            PaperweightPlatformAdapter.sendChunk(this, serverLevel, chunkX, chunkZ);
+            PaperweightPlatformAdapter.sendChunk(new IntPair(chunkX, chunkZ), serverLevel, chunkX, chunkZ);
         }
     }
 

worldedit-bukkit/adapters/adapter-1_20_2/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R2/PaperweightPlatformAdapter.java

@@ -7,8 +7,8 @@ import com.fastasyncworldedit.bukkit.adapter.NMSAdapter;
 import com.fastasyncworldedit.core.Fawe;
 import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.util.MathMan;
-import com.fastasyncworldedit.core.util.ReflectionUtils;
 import com.fastasyncworldedit.core.util.TaskManager;
 import com.mojang.datafixers.util.Either;
 import com.sk89q.worldedit.bukkit.WorldEditPlugin;
@@ -243,15 +243,14 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     static boolean setSectionAtomic(
+            String worldName,
+            IntPair pair,
             LevelChunkSection[] sections,
             LevelChunkSection expected,
             LevelChunkSection value,
             int layer
     ) {
-        if (layer >= 0 && layer < sections.length) {
+        return NMSAdapter.setSectionAtomic(worldName, pair, sections, expected, value, layer);
-            return ReflectionUtils.compareAndSet(sections, expected, value, layer);
-        }
-        return false;
     }
 
     // There is no point in having a functional semaphore for paper servers.
@@ -349,7 +348,7 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     @SuppressWarnings("deprecation")
-    public static void sendChunk(Object chunk, ServerLevel nmsWorld, int chunkX, int chunkZ) {
+    public static void sendChunk(IntPair pair, ServerLevel nmsWorld, int chunkX, int chunkZ) {
         ChunkHolder chunkHolder = getPlayerChunk(nmsWorld, chunkX, chunkZ);
         if (chunkHolder == null) {
             return;
@@ -370,26 +369,35 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
         if (levelChunk == null) {
             return;
         }
+        StampLockHolder lockHolder = new StampLockHolder();
+        NMSAdapter.beginChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
+        if (lockHolder.chunkLock == null) {
+            return;
+        }
         MinecraftServer.getServer().execute(() -> {
-            ClientboundLevelChunkWithLightPacket packet;
+            try {
-            if (PaperLib.isPaper()) {
+                ClientboundLevelChunkWithLightPacket packet;
-                packet = new ClientboundLevelChunkWithLightPacket(
+                if (PaperLib.isPaper()) {
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null,
+                            null,
-                        false // last false is to not bother with x-ray
+                            null,
-                );
+                            false // last false is to not bother with x-ray
-            } else {
+                    );
-                // deprecated on paper - deprecation suppressed
+                } else {
-                packet = new ClientboundLevelChunkWithLightPacket(
+                    // deprecated on paper - deprecation suppressed
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null
+                            null,
-                );
+                            null
+                    );
+                }
+                nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
+            } finally {
+                NMSAdapter.endChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
             }
-            nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
         });
     }
 

worldedit-bukkit/adapters/adapter-1_20_2/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R2/PaperweightStarlightRelighter.java

@@ -2,6 +2,7 @@ package com.sk89q.worldedit.bukkit.adapter.impl.fawe.v1_20_R2;
 
 import com.fastasyncworldedit.bukkit.adapter.StarlightRelighter;
 import com.fastasyncworldedit.core.configuration.Settings;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.queue.IQueueExtent;
 import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerLevel;
@@ -67,7 +68,7 @@ public class PaperweightStarlightRelighter extends StarlightRelighter<ServerLeve
             int x = pos.x;
             int z = pos.z;
             if (delay) { // we still need to send the block changes of that chunk
-                PaperweightPlatformAdapter.sendChunk(pos, serverLevel, x, z);
+                PaperweightPlatformAdapter.sendChunk(new IntPair(x, z), serverLevel, x, z);
             }
             serverLevel.getChunkSource().removeTicketAtLevel(FAWE_TICKET, pos, LIGHT_LEVEL, Unit.INSTANCE);
         }

worldedit-bukkit/adapters/adapter-1_20_4/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R3/PaperweightGetBlocks.java

@@ -7,6 +7,7 @@ import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.configuration.Settings;
 import com.fastasyncworldedit.core.extent.processor.heightmap.HeightMapType;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.nbt.FaweCompoundTag;
 import com.fastasyncworldedit.core.queue.IChunkGet;
 import com.fastasyncworldedit.core.queue.IChunkSet;
@@ -106,6 +107,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     private final ServerLevel serverLevel;
     private final int chunkX;
     private final int chunkZ;
+    private final IntPair chunkPos;
     private final int minHeight;
     private final int maxHeight;
     private final int minSectionPosition;
@@ -140,6 +142,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
         this.blockLight = new DataLayer[getSectionCount()];
         this.biomeRegistry = serverLevel.registryAccess().registryOrThrow(BIOME);
         this.biomeHolderIdMap = biomeRegistry.asHolderIdMap();
+        this.chunkPos = new IntPair(chunkX, chunkZ);
     }
 
     public int getChunkX() {
@@ -425,7 +428,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             throw new IllegalStateException("Attempted to call chunk GET but chunk was not call-locked.");
         }
         forceLoadSections = false;
-        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(levelChunk) : null;
+        LevelChunk nmsChunk = ensureLoaded(serverLevel, chunkX, chunkZ);
+        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(nmsChunk) : null;
         if (createCopy) {
             if (copies.containsKey(copyKey)) {
                 throw new IllegalStateException("Copy key already used.");
@@ -433,9 +437,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             copies.put(copyKey, copy);
         }
         try {
-            ServerLevel nmsWorld = serverLevel;
-            LevelChunk nmsChunk = ensureLoaded(nmsWorld, chunkX, chunkZ);
-
             // Remove existing tiles. Create a copy so that we can remove blocks
             Map<BlockPos, BlockEntity> chunkTiles = new HashMap<>(nmsChunk.getBlockEntities());
             List<BlockEntity> beacons = null;
@@ -507,6 +508,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                             biomeData
                                     );
                                     if (PaperweightPlatformAdapter.setSectionAtomic(
+                                            serverLevel.getWorld().getName(),
+                                            chunkPos,
                                             levelChunkSections,
                                             null,
                                             newSection,
@@ -584,6 +587,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeData
                             );
                             if (PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
                                     levelChunkSections,
                                     null,
                                     newSection,
@@ -649,6 +654,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeData != null ? biomeData : (PalettedContainer<Holder<Biome>>) existingSection.getBiomes()
                             );
                             if (!PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
                                     levelChunkSections,
                                     existingSection,
                                     newSection,
@@ -722,7 +729,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                         }
                         if (Settings.settings().EXPERIMENTAL.REMOVE_ENTITY_FROM_WORLD_ON_CHUNK_FAIL) {
                             for (UUID uuid : entityRemoves) {
-                                Entity entity = nmsWorld.getEntities().get(uuid);
+                                Entity entity = serverLevel.getEntities().get(uuid);
                                 if (entity != null) {
                                     removeEntity(entity);
                                 }
@@ -761,7 +768,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
 
                             EntityType<?> type = EntityType.byString(id).orElse(null);
                             if (type != null) {
-                                Entity entity = type.create(nmsWorld);
+                                Entity entity = type.create(serverLevel);
                                 if (entity != null) {
                                     final net.minecraft.nbt.CompoundTag tag = (net.minecraft.nbt.CompoundTag) adapter.fromNativeLin(linTag);
                                     for (final String name : Constants.NO_COPY_ENTITY_NBT_FIELDS) {
@@ -770,11 +777,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     entity.load(tag);
                                     entity.absMoveTo(x, y, z, yaw, pitch);
                                     entity.setUUID(NbtUtils.uuid(nativeTag));
-                                    if (!nmsWorld.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
+                                    if (!serverLevel.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
                                         LOGGER.warn(
                                                 "Error creating entity of type `{}` in world `{}` at location `{},{},{}`",
                                                 id,
-                                                nmsWorld.getWorld().getName(),
+                                                serverLevel.getWorld().getName(),
                                                 x,
                                                 y,
                                                 z
@@ -804,11 +811,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                             final int z = blockHash.z() + bz;
                             final BlockPos pos = new BlockPos(x, y, z);
 
-                            synchronized (nmsWorld) {
+                            synchronized (serverLevel) {
-                                BlockEntity tileEntity = nmsWorld.getBlockEntity(pos);
+                                BlockEntity tileEntity = serverLevel.getBlockEntity(pos);
                                 if (tileEntity == null || tileEntity.isRemoved()) {
-                                    nmsWorld.removeBlockEntity(pos);
+                                    serverLevel.removeBlockEntity(pos);
-                                    tileEntity = nmsWorld.getBlockEntity(pos);
+                                    tileEntity = serverLevel.getBlockEntity(pos);
                                 }
                                 if (tileEntity != null) {
                                     final net.minecraft.nbt.CompoundTag tag = (CompoundTag) adapter.fromNativeLin(nativeTag.linTag());
@@ -827,7 +834,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                     callback = null;
                 } else {
                     int finalMask = bitMask != 0 ? bitMask : lightUpdate ? set.getBitMask() : 0;
-                    boolean finalLightUpdate = lightUpdate;
                     callback = () -> {
                         // Set Modified
                         nmsChunk.setLightCorrect(true); // Set Modified
@@ -932,7 +938,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
 
     @Override
     public void send() {
-        PaperweightPlatformAdapter.sendChunk(this, serverLevel, chunkX, chunkZ);
+        PaperweightPlatformAdapter.sendChunk(new IntPair(chunkX, chunkZ), serverLevel, chunkX, chunkZ);
     }
 
     /**

worldedit-bukkit/adapters/adapter-1_20_4/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R3/PaperweightPlatformAdapter.java

@@ -7,8 +7,8 @@ import com.fastasyncworldedit.bukkit.adapter.NMSAdapter;
 import com.fastasyncworldedit.core.Fawe;
 import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.util.MathMan;
-import com.fastasyncworldedit.core.util.ReflectionUtils;
 import com.fastasyncworldedit.core.util.TaskManager;
 import com.mojang.datafixers.util.Either;
 import com.sk89q.worldedit.bukkit.WorldEditPlugin;
@@ -243,15 +243,14 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     static boolean setSectionAtomic(
+            String worldName,
+            IntPair pair,
             LevelChunkSection[] sections,
             LevelChunkSection expected,
             LevelChunkSection value,
             int layer
     ) {
-        if (layer >= 0 && layer < sections.length) {
+        return NMSAdapter.setSectionAtomic(worldName, pair, sections, expected, value, layer);
-            return ReflectionUtils.compareAndSet(sections, expected, value, layer);
-        }
-        return false;
     }
 
     // There is no point in having a functional semaphore for paper servers.
@@ -349,7 +348,7 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     @SuppressWarnings("deprecation")
-    public static void sendChunk(Object chunk, ServerLevel nmsWorld, int chunkX, int chunkZ) {
+    public static void sendChunk(IntPair pair, ServerLevel nmsWorld, int chunkX, int chunkZ) {
         ChunkHolder chunkHolder = getPlayerChunk(nmsWorld, chunkX, chunkZ);
         if (chunkHolder == null) {
             return;
@@ -370,26 +369,35 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
         if (levelChunk == null) {
             return;
         }
+        StampLockHolder lockHolder = new StampLockHolder();
+        NMSAdapter.beginChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
+        if (lockHolder.chunkLock == null) {
+            return;
+        }
         MinecraftServer.getServer().execute(() -> {
-            ClientboundLevelChunkWithLightPacket packet;
+            try {
-            if (PaperLib.isPaper()) {
+                ClientboundLevelChunkWithLightPacket packet;
-                packet = new ClientboundLevelChunkWithLightPacket(
+                if (PaperLib.isPaper()) {
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null,
+                            null,
-                        false // last false is to not bother with x-ray
+                            null,
-                );
+                            false // last false is to not bother with x-ray
-            } else {
+                    );
-                // deprecated on paper - deprecation suppressed
+                } else {
-                packet = new ClientboundLevelChunkWithLightPacket(
+                    // deprecated on paper - deprecation suppressed
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null
+                            null,
-                );
+                            null
+                    );
+                }
+                nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
+            } finally {
+                NMSAdapter.endChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
             }
-            nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
         });
     }
 

worldedit-bukkit/adapters/adapter-1_20_4/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R3/PaperweightStarlightRelighter.java

@@ -2,6 +2,7 @@ package com.sk89q.worldedit.bukkit.adapter.impl.fawe.v1_20_R3;
 
 import com.fastasyncworldedit.bukkit.adapter.StarlightRelighter;
 import com.fastasyncworldedit.core.configuration.Settings;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.queue.IQueueExtent;
 import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerLevel;
@@ -67,7 +68,7 @@ public class PaperweightStarlightRelighter extends StarlightRelighter<ServerLeve
             int x = pos.x;
             int z = pos.z;
             if (delay) { // we still need to send the block changes of that chunk
-                PaperweightPlatformAdapter.sendChunk(pos, serverLevel, x, z);
+                PaperweightPlatformAdapter.sendChunk(new IntPair(x, z), serverLevel, x, z);
             }
             serverLevel.getChunkSource().removeTicketAtLevel(FAWE_TICKET, pos, LIGHT_LEVEL, Unit.INSTANCE);
         }

worldedit-bukkit/adapters/adapter-1_20_5/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R4/PaperweightGetBlocks.java

@@ -7,6 +7,7 @@ import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.configuration.Settings;
 import com.fastasyncworldedit.core.extent.processor.heightmap.HeightMapType;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.nbt.FaweCompoundTag;
 import com.fastasyncworldedit.core.queue.IChunkGet;
 import com.fastasyncworldedit.core.queue.IChunkSet;
@@ -107,6 +108,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     private final ServerLevel serverLevel;
     private final int chunkX;
     private final int chunkZ;
+    private final IntPair chunkPos;
     private final int minHeight;
     private final int maxHeight;
     private final int minSectionPosition;
@@ -141,6 +143,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
         this.blockLight = new DataLayer[getSectionCount()];
         this.biomeRegistry = serverLevel.registryAccess().registryOrThrow(BIOME);
         this.biomeHolderIdMap = biomeRegistry.asHolderIdMap();
+        this.chunkPos = new IntPair(chunkX, chunkZ);
     }
 
     public int getChunkX() {
@@ -426,7 +429,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             throw new IllegalStateException("Attempted to call chunk GET but chunk was not call-locked.");
         }
         forceLoadSections = false;
-        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(levelChunk) : null;
+        LevelChunk nmsChunk = ensureLoaded(serverLevel, chunkX, chunkZ);
+        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(nmsChunk) : null;
         if (createCopy) {
             if (copies.containsKey(copyKey)) {
                 throw new IllegalStateException("Copy key already used.");
@@ -434,9 +438,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             copies.put(copyKey, copy);
         }
         try {
-            ServerLevel nmsWorld = serverLevel;
-            LevelChunk nmsChunk = ensureLoaded(nmsWorld, chunkX, chunkZ);
-
             // Remove existing tiles. Create a copy so that we can remove blocks
             Map<BlockPos, BlockEntity> chunkTiles = new HashMap<>(nmsChunk.getBlockEntities());
             List<BlockEntity> beacons = null;
@@ -508,6 +509,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                             biomeData
                                     );
                                     if (PaperweightPlatformAdapter.setSectionAtomic(
+                                            serverLevel.getWorld().getName(),
+                                            chunkPos,
                                             levelChunkSections,
                                             null,
                                             newSection,
@@ -585,6 +588,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeData
                             );
                             if (PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
                                     levelChunkSections,
                                     null,
                                     newSection,
@@ -649,7 +654,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeRegistry,
                                     biomeData != null ? biomeData : (PalettedContainer<Holder<Biome>>) existingSection.getBiomes()
                             );
-                            if (!PaperweightPlatformAdapter.setSectionAtomic(levelChunkSections, existingSection,
+                            if (!PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
+                                    levelChunkSections,
+                                    existingSection,
                                     newSection,
                                     getSectionIndex
                             )) {
@@ -721,7 +730,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                         }
                         if (Settings.settings().EXPERIMENTAL.REMOVE_ENTITY_FROM_WORLD_ON_CHUNK_FAIL) {
                             for (UUID uuid : entityRemoves) {
-                                Entity entity = nmsWorld.getEntities().get(uuid);
+                                Entity entity = serverLevel.getEntities().get(uuid);
                                 if (entity != null) {
                                     removeEntity(entity);
                                 }
@@ -760,7 +769,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
 
                             EntityType<?> type = EntityType.byString(id).orElse(null);
                             if (type != null) {
-                                Entity entity = type.create(nmsWorld);
+                                Entity entity = type.create(serverLevel);
                                 if (entity != null) {
                                     final net.minecraft.nbt.CompoundTag tag = (net.minecraft.nbt.CompoundTag) adapter.fromNativeLin(linTag);
                                     for (final String name : Constants.NO_COPY_ENTITY_NBT_FIELDS) {
@@ -769,11 +778,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     entity.load(tag);
                                     entity.absMoveTo(x, y, z, yaw, pitch);
                                     entity.setUUID(NbtUtils.uuid(nativeTag));
-                                    if (!nmsWorld.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
+                                    if (!serverLevel.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
                                         LOGGER.warn(
                                                 "Error creating entity of type `{}` in world `{}` at location `{},{},{}`",
                                                 id,
-                                                nmsWorld.getWorld().getName(),
+                                                serverLevel.getWorld().getName(),
                                                 x,
                                                 y,
                                                 z
@@ -803,11 +812,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                             final int z = blockHash.z() + bz;
                             final BlockPos pos = new BlockPos(x, y, z);
 
-                            synchronized (nmsWorld) {
+                            synchronized (serverLevel) {
-                                BlockEntity tileEntity = nmsWorld.getBlockEntity(pos);
+                                BlockEntity tileEntity = serverLevel.getBlockEntity(pos);
                                 if (tileEntity == null || tileEntity.isRemoved()) {
-                                    nmsWorld.removeBlockEntity(pos);
+                                    serverLevel.removeBlockEntity(pos);
-                                    tileEntity = nmsWorld.getBlockEntity(pos);
+                                    tileEntity = serverLevel.getBlockEntity(pos);
                                 }
                                 if (tileEntity != null) {
                                     final net.minecraft.nbt.CompoundTag tag = (CompoundTag) adapter.fromNativeLin(nativeTag.linTag());
@@ -826,7 +835,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                     callback = null;
                 } else {
                     int finalMask = bitMask != 0 ? bitMask : lightUpdate ? set.getBitMask() : 0;
-                    boolean finalLightUpdate = lightUpdate;
                     callback = () -> {
                         // Set Modified
                         nmsChunk.setLightCorrect(true); // Set Modified
@@ -932,7 +940,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     @Override
     public void send() {
         synchronized (sendLock) {
-            PaperweightPlatformAdapter.sendChunk(this, serverLevel, chunkX, chunkZ);
+            PaperweightPlatformAdapter.sendChunk(new IntPair(chunkX, chunkZ), serverLevel, chunkX, chunkZ);
         }
     }
 

worldedit-bukkit/adapters/adapter-1_20_5/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R4/PaperweightPlatformAdapter.java

@@ -7,9 +7,10 @@ import com.fastasyncworldedit.bukkit.adapter.NMSAdapter;
 import com.fastasyncworldedit.core.Fawe;
 import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.util.MathMan;
-import com.fastasyncworldedit.core.util.ReflectionUtils;
 import com.fastasyncworldedit.core.util.TaskManager;
+import com.mojang.datafixers.util.Either;
 import com.sk89q.worldedit.bukkit.WorldEditPlugin;
 import com.sk89q.worldedit.bukkit.adapter.BukkitImplAdapter;
 import com.sk89q.worldedit.bukkit.adapter.Refraction;
@@ -76,6 +77,7 @@ import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
@@ -241,15 +243,14 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     static boolean setSectionAtomic(
+            String worldName,
+            IntPair pair,
             LevelChunkSection[] sections,
             LevelChunkSection expected,
             LevelChunkSection value,
             int layer
     ) {
-        if (layer >= 0 && layer < sections.length) {
+        return NMSAdapter.setSectionAtomic(worldName, pair, sections, expected, value, layer);
-            return ReflectionUtils.compareAndSet(sections, expected, value, layer);
-        }
-        return false;
     }
 
     // There is no point in having a functional semaphore for paper servers.
@@ -347,7 +348,7 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     @SuppressWarnings("deprecation")
-    public static void sendChunk(Object chunk, ServerLevel nmsWorld, int chunkX, int chunkZ) {
+    public static void sendChunk(IntPair pair, ServerLevel nmsWorld, int chunkX, int chunkZ) {
         ChunkHolder chunkHolder = getPlayerChunk(nmsWorld, chunkX, chunkZ);
         if (chunkHolder == null) {
             return;
@@ -360,32 +361,43 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
                     .getChunkSource()
                     .getChunkAtIfLoadedImmediately(chunkX, chunkZ);
         } else {
-            levelChunk = chunkHolder.getTickingChunkFuture()
+            levelChunk = ((Optional<LevelChunk>) ((Either) chunkHolder
-                    .getNow(ChunkHolder.UNLOADED_LEVEL_CHUNK).orElse(null);
+                    .getTickingChunkFuture() // method is not present with new paper chunk system
+                    .getNow(ChunkHolder.UNLOADED_LEVEL_CHUNK)).left())
+                    .orElse(null);
         }
         if (levelChunk == null) {
             return;
         }
+        StampLockHolder lockHolder = new StampLockHolder();
+        NMSAdapter.beginChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
+        if (lockHolder.chunkLock == null) {
+            return;
+        }
         MinecraftServer.getServer().execute(() -> {
-            ClientboundLevelChunkWithLightPacket packet;
+            try {
-            if (PaperLib.isPaper()) {
+                ClientboundLevelChunkWithLightPacket packet;
-                packet = new ClientboundLevelChunkWithLightPacket(
+                if (PaperLib.isPaper()) {
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null,
+                            null,
-                        false // last false is to not bother with x-ray
+                            null,
-                );
+                            false // last false is to not bother with x-ray
-            } else {
+                    );
-                // deprecated on paper - deprecation suppressed
+                } else {
-                packet = new ClientboundLevelChunkWithLightPacket(
+                    // deprecated on paper - deprecation suppressed
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null
+                            null,
-                );
+                            null
+                    );
+                }
+                nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
+            } finally {
+                NMSAdapter.endChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
             }
-            nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
         });
     }
 

worldedit-bukkit/adapters/adapter-1_20_5/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_20_R4/PaperweightStarlightRelighter.java

@@ -2,6 +2,7 @@ package com.sk89q.worldedit.bukkit.adapter.impl.fawe.v1_20_R4;
 
 import com.fastasyncworldedit.bukkit.adapter.StarlightRelighter;
 import com.fastasyncworldedit.core.configuration.Settings;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.queue.IQueueExtent;
 import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerLevel;
@@ -67,7 +68,7 @@ public class PaperweightStarlightRelighter extends StarlightRelighter<ServerLeve
             int x = pos.x;
             int z = pos.z;
             if (delay) { // we still need to send the block changes of that chunk
-                PaperweightPlatformAdapter.sendChunk(pos, serverLevel, x, z);
+                PaperweightPlatformAdapter.sendChunk(new IntPair(x, z), serverLevel, x, z);
             }
             serverLevel.getChunkSource().removeTicketAtLevel(FAWE_TICKET, pos, LIGHT_LEVEL, Unit.INSTANCE);
         }

worldedit-bukkit/adapters/adapter-1_21/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_21_R1/PaperweightGetBlocks.java

@@ -7,6 +7,7 @@ import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.configuration.Settings;
 import com.fastasyncworldedit.core.extent.processor.heightmap.HeightMapType;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.nbt.FaweCompoundTag;
 import com.fastasyncworldedit.core.queue.IChunkGet;
 import com.fastasyncworldedit.core.queue.IChunkSet;
@@ -107,6 +108,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     private final ServerLevel serverLevel;
     private final int chunkX;
     private final int chunkZ;
+    private final IntPair chunkPos;
     private final int minHeight;
     private final int maxHeight;
     private final int minSectionPosition;
@@ -141,6 +143,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
         this.blockLight = new DataLayer[getSectionCount()];
         this.biomeRegistry = serverLevel.registryAccess().registryOrThrow(BIOME);
         this.biomeHolderIdMap = biomeRegistry.asHolderIdMap();
+        this.chunkPos = new IntPair(chunkX, chunkZ);
     }
 
     public int getChunkX() {
@@ -427,7 +430,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             throw new IllegalStateException("Attempted to call chunk GET but chunk was not call-locked.");
         }
         forceLoadSections = false;
-        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(levelChunk) : null;
+        LevelChunk nmsChunk = ensureLoaded(serverLevel, chunkX, chunkZ);
+        PaperweightGetBlocks_Copy copy = createCopy ? new PaperweightGetBlocks_Copy(nmsChunk) : null;
         if (createCopy) {
             if (copies.containsKey(copyKey)) {
                 throw new IllegalStateException("Copy key already used.");
@@ -435,9 +439,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
             copies.put(copyKey, copy);
         }
         try {
-            ServerLevel nmsWorld = serverLevel;
-            LevelChunk nmsChunk = ensureLoaded(nmsWorld, chunkX, chunkZ);
-
             // Remove existing tiles. Create a copy so that we can remove blocks
             Map<BlockPos, BlockEntity> chunkTiles = new HashMap<>(nmsChunk.getBlockEntities());
             List<BlockEntity> beacons = null;
@@ -509,6 +510,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                             biomeData
                                     );
                                     if (PaperweightPlatformAdapter.setSectionAtomic(
+                                            serverLevel.getWorld().getName(),
+                                            chunkPos,
                                             levelChunkSections,
                                             null,
                                             newSection,
@@ -583,6 +586,8 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeData
                             );
                             if (PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
                                     levelChunkSections,
                                     null,
                                     newSection,
@@ -644,7 +649,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     biomeRegistry,
                                     biomeData != null ? biomeData : (PalettedContainer<Holder<Biome>>) existingSection.getBiomes()
                             );
-                            if (!PaperweightPlatformAdapter.setSectionAtomic(levelChunkSections, existingSection,
+                            if (!PaperweightPlatformAdapter.setSectionAtomic(
+                                    serverLevel.getWorld().getName(),
+                                    chunkPos,
+                                    levelChunkSections,
+                                    existingSection,
                                     newSection,
                                     getSectionIndex
                             )) {
@@ -716,7 +725,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                         }
                         if (Settings.settings().EXPERIMENTAL.REMOVE_ENTITY_FROM_WORLD_ON_CHUNK_FAIL) {
                             for (UUID uuid : entityRemoves) {
-                                Entity entity = nmsWorld.getEntities().get(uuid);
+                                Entity entity = serverLevel.getEntities().get(uuid);
                                 if (entity != null) {
                                     removeEntity(entity);
                                 }
@@ -755,7 +764,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
 
                             EntityType<?> type = EntityType.byString(id).orElse(null);
                             if (type != null) {
-                                Entity entity = type.create(nmsWorld);
+                                Entity entity = type.create(serverLevel);
                                 if (entity != null) {
                                     final CompoundTag tag = (CompoundTag) adapter.fromNativeLin(linTag);
                                     for (final String name : Constants.NO_COPY_ENTITY_NBT_FIELDS) {
@@ -764,11 +773,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                                     entity.load(tag);
                                     entity.absMoveTo(x, y, z, yaw, pitch);
                                     entity.setUUID(NbtUtils.uuid(nativeTag));
-                                    if (!nmsWorld.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
+                                    if (!serverLevel.addFreshEntity(entity, CreatureSpawnEvent.SpawnReason.CUSTOM)) {
                                         LOGGER.warn(
                                                 "Error creating entity of type `{}` in world `{}` at location `{},{},{}`",
                                                 id,
-                                                nmsWorld.getWorld().getName(),
+                                                serverLevel.getWorld().getName(),
                                                 x,
                                                 y,
                                                 z
@@ -798,11 +807,11 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                             final int z = blockHash.z() + bz;
                             final BlockPos pos = new BlockPos(x, y, z);
 
-                            synchronized (nmsWorld) {
+                            synchronized (serverLevel) {
-                                BlockEntity tileEntity = nmsWorld.getBlockEntity(pos);
+                                BlockEntity tileEntity = serverLevel.getBlockEntity(pos);
                                 if (tileEntity == null || tileEntity.isRemoved()) {
-                                    nmsWorld.removeBlockEntity(pos);
+                                    serverLevel.removeBlockEntity(pos);
-                                    tileEntity = nmsWorld.getBlockEntity(pos);
+                                    tileEntity = serverLevel.getBlockEntity(pos);
                                 }
                                 if (tileEntity != null) {
                                     final CompoundTag tag = (CompoundTag) adapter.fromNativeLin(nativeTag.linTag());
@@ -821,7 +830,6 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
                     callback = null;
                 } else {
                     int finalMask = bitMask != 0 ? bitMask : lightUpdate ? set.getBitMask() : 0;
-                    boolean finalLightUpdate = lightUpdate;
                     callback = () -> {
                         // Set Modified
                         nmsChunk.setLightCorrect(true); // Set Modified
@@ -927,7 +935,7 @@ public class PaperweightGetBlocks extends CharGetBlocks implements BukkitGetBloc
     @Override
     public void send() {
         synchronized (sendLock) {
-            PaperweightPlatformAdapter.sendChunk(this, serverLevel, chunkX, chunkZ);
+            PaperweightPlatformAdapter.sendChunk(new IntPair(chunkX, chunkZ), serverLevel, chunkX, chunkZ);
         }
     }
 

worldedit-bukkit/adapters/adapter-1_21/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_21_R1/PaperweightPlatformAdapter.java

@@ -8,9 +8,10 @@ import com.fastasyncworldedit.bukkit.adapter.NMSAdapter;
 import com.fastasyncworldedit.core.Fawe;
 import com.fastasyncworldedit.core.FaweCache;
 import com.fastasyncworldedit.core.math.BitArrayUnstretched;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.util.MathMan;
-import com.fastasyncworldedit.core.util.ReflectionUtils;
 import com.fastasyncworldedit.core.util.TaskManager;
+import com.mojang.datafixers.util.Either;
 import com.sk89q.worldedit.bukkit.WorldEditPlugin;
 import com.sk89q.worldedit.bukkit.adapter.BukkitImplAdapter;
 import com.sk89q.worldedit.bukkit.adapter.Refraction;
@@ -31,7 +32,6 @@ import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerLevel;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.util.BitStorage;
-import net.minecraft.util.ExceptionCollector;
 import net.minecraft.util.SimpleBitStorage;
 import net.minecraft.util.ThreadingDetector;
 import net.minecraft.util.Unit;
@@ -76,6 +76,7 @@ import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.TimeUnit;
@@ -226,15 +227,14 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     static boolean setSectionAtomic(
+            String worldName,
+            IntPair pair,
             LevelChunkSection[] sections,
             LevelChunkSection expected,
             LevelChunkSection value,
             int layer
     ) {
-        if (layer >= 0 && layer < sections.length) {
+        return NMSAdapter.setSectionAtomic(worldName, pair, sections, expected, value, layer);
-            return ReflectionUtils.compareAndSet(sections, expected, value, layer);
-        }
-        return false;
     }
 
     // There is no point in having a functional semaphore for paper servers.
@@ -332,7 +332,7 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
     }
 
     @SuppressWarnings("deprecation")
-    public static void sendChunk(Object chunk, ServerLevel nmsWorld, int chunkX, int chunkZ) {
+    public static void sendChunk(IntPair pair, ServerLevel nmsWorld, int chunkX, int chunkZ) {
         ChunkHolder chunkHolder = getPlayerChunk(nmsWorld, chunkX, chunkZ);
         if (chunkHolder == null) {
             return;
@@ -345,32 +345,43 @@ public final class PaperweightPlatformAdapter extends NMSAdapter {
                     .getChunkSource()
                     .getChunkAtIfLoadedImmediately(chunkX, chunkZ);
         } else {
-            levelChunk = chunkHolder.getTickingChunkFuture()
+            levelChunk = ((Optional<LevelChunk>) ((Either) chunkHolder
-                    .getNow(ChunkHolder.UNLOADED_LEVEL_CHUNK).orElse(null);
+                    .getTickingChunkFuture() // method is not present with new paper chunk system
+                    .getNow(ChunkHolder.UNLOADED_LEVEL_CHUNK)).left())
+                    .orElse(null);
         }
         if (levelChunk == null) {
             return;
         }
+        StampLockHolder lockHolder = new StampLockHolder();
+        NMSAdapter.beginChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
+        if (lockHolder.chunkLock == null) {
+            return;
+        }
         MinecraftServer.getServer().execute(() -> {
-            ClientboundLevelChunkWithLightPacket packet;
+            try {
-            if (PaperLib.isPaper()) {
+                ClientboundLevelChunkWithLightPacket packet;
-                packet = new ClientboundLevelChunkWithLightPacket(
+                if (PaperLib.isPaper()) {
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null,
+                            null,
-                        false // last false is to not bother with x-ray
+                            null,
-                );
+                            false // last false is to not bother with x-ray
-            } else {
+                    );
-                // deprecated on paper - deprecation suppressed
+                } else {
-                packet = new ClientboundLevelChunkWithLightPacket(
+                    // deprecated on paper - deprecation suppressed
-                        levelChunk,
+                    packet = new ClientboundLevelChunkWithLightPacket(
-                        nmsWorld.getChunkSource().getLightEngine(),
+                            levelChunk,
-                        null,
+                            nmsWorld.getChunkSource().getLightEngine(),
-                        null
+                            null,
-                );
+                            null
+                    );
+                }
+                nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
+            } finally {
+                NMSAdapter.endChunkPacketSend(nmsWorld.getWorld().getName(), pair, lockHolder);
             }
-            nearbyPlayers(nmsWorld, coordIntPair).forEach(p -> p.connection.send(packet));
         });
     }
 

worldedit-bukkit/adapters/adapter-1_21/src/main/java/com/sk89q/worldedit/bukkit/adapter/impl/fawe/v1_21_R1/PaperweightStarlightRelighter.java

@@ -2,6 +2,7 @@ package com.sk89q.worldedit.bukkit.adapter.impl.fawe.v1_21_R1;
 
 import com.fastasyncworldedit.bukkit.adapter.StarlightRelighter;
 import com.fastasyncworldedit.core.configuration.Settings;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.queue.IQueueExtent;
 import net.minecraft.server.level.ChunkMap;
 import net.minecraft.server.level.ServerLevel;
@@ -70,7 +71,7 @@ public class PaperweightStarlightRelighter extends StarlightRelighter<ServerLeve
             int x = pos.x;
             int z = pos.z;
             if (delay) { // we still need to send the block changes of that chunk
-                PaperweightPlatformAdapter.sendChunk(pos, serverLevel, x, z);
+                PaperweightPlatformAdapter.sendChunk(new IntPair(x, z), serverLevel, x, z);
             }
             serverLevel.getChunkSource().removeTicketAtLevel(FAWE_TICKET, pos, LIGHT_LEVEL, Unit.INSTANCE);
         }

worldedit-bukkit/src/main/java/com/fastasyncworldedit/bukkit/FaweBukkitWorld.java

@@ -0,0 +1,67 @@
+package com.fastasyncworldedit.bukkit;
+
+import com.fastasyncworldedit.bukkit.adapter.NMSAdapter;
+import com.fastasyncworldedit.bukkit.util.WorldUnloadedException;
+import com.fastasyncworldedit.core.math.IntPair;
+import com.sk89q.worldedit.bukkit.BukkitWorld;
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+
+import java.lang.ref.WeakReference;
+import java.util.Collections;
+import java.util.Map;
+import java.util.WeakHashMap;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class FaweBukkitWorld extends BukkitWorld {
+
+    private static final Map<World, FaweBukkitWorld> CACHE = Collections.synchronizedMap(new WeakHashMap<>());
+
+    private final ConcurrentHashMap<IntPair, NMSAdapter.ChunkSendLock> SENDING_CHUNKS = new ConcurrentHashMap<>();
+
+    /**
+     * Construct the object.
+     *
+     * @param world the world
+     */
+    private FaweBukkitWorld(final World world) {
+        super(world);
+    }
+
+    public static FaweBukkitWorld of(World world) {
+        return CACHE.compute(world, (__, val) -> {
+            if (val == null) {
+                return new FaweBukkitWorld(world);
+            }
+            val.updateReference();
+            return val;
+        });
+    }
+
+    public static FaweBukkitWorld of(String worldName) {
+        World world = Bukkit.getWorld(worldName);
+        if (world == null) {
+            throw new UnsupportedOperationException("Unable to find org.bukkit.World instance for " + worldName + ". Is it loaded?");
+        }
+        return of(world);
+    }
+
+    public static ConcurrentHashMap<IntPair, NMSAdapter.ChunkSendLock> getWorldSendingChunksMap(FaweBukkitWorld world) {
+        return world.SENDING_CHUNKS;
+    }
+
+    public static ConcurrentHashMap<IntPair, NMSAdapter.ChunkSendLock> getWorldSendingChunksMap(String worldName) {
+        return of(worldName).SENDING_CHUNKS;
+    }
+
+    private void updateReference() {
+        World world = getWorld();
+        World bukkitWorld = Bukkit.getWorld(worldNameRef);
+        if (bukkitWorld == null) {
+            throw new WorldUnloadedException(worldNameRef);
+        } else if (bukkitWorld != world) {
+            worldRef = new WeakReference<>(bukkitWorld);
+        }
+    }
+
+}

worldedit-bukkit/src/main/java/com/fastasyncworldedit/bukkit/adapter/NMSAdapter.java

@@ -1,12 +1,17 @@
 package com.fastasyncworldedit.bukkit.adapter;
 
+import com.fastasyncworldedit.bukkit.FaweBukkitWorld;
 import com.fastasyncworldedit.core.FAWEPlatformAdapterImpl;
+import com.fastasyncworldedit.core.math.IntPair;
 import com.fastasyncworldedit.core.queue.IChunkGet;
 import com.fastasyncworldedit.core.util.MathMan;
+import com.fastasyncworldedit.core.util.ReflectionUtils;
 import com.sk89q.worldedit.world.block.BlockTypesCache;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.locks.StampedLock;
 import java.util.function.Function;
 
 public class NMSAdapter implements FAWEPlatformAdapterImpl {
@@ -140,4 +145,118 @@ public class NMSAdapter implements FAWEPlatformAdapterImpl {
         ((BukkitGetBlocks) chunk).send();
     }
 
+    /**
+     * Atomically set the given chunk section to the chunk section array stored in the chunk, given the expected existing chunk
+     * section instance at the given layer position.
+     * <p>
+     * Acquires a (FAWE-implemented only) write-lock on the chunk packet lock, waiting if required before writing, then freeing
+     * the lock. Also sets a boolean to indicate a write is waiting and therefore reads should not occur.
+     * <p>
+     * Utilises ConcurrentHashMap#compute for easy synchronisation for all of the above. Only tryWriteLock is used in blocks
+     * synchronised using ConcurrentHashMap methods.
+     *
+     * @since TODO
+     */
+    protected static <LevelChunkSection> boolean setSectionAtomic(
+            String worldName,
+            IntPair pair,
+            LevelChunkSection[] sections,
+            LevelChunkSection expected,
+            LevelChunkSection value,
+            int layer
+    ) {
+        if (layer < 0 || layer >= sections.length) {
+            return false;
+        }
+        StampLockHolder holder = new StampLockHolder();
+        ConcurrentHashMap<IntPair, ChunkSendLock> chunks = FaweBukkitWorld.getWorldSendingChunksMap(worldName);
+        chunks.compute(pair, (k, lock) -> {
+            if (lock == null) {
+                lock = new ChunkSendLock();
+            } else if (lock.writeWaiting) {
+                throw new IllegalStateException("Attempting to write chunk section when write is already ongoing?!");
+            }
+            holder.stamp = lock.lock.tryWriteLock();
+            holder.chunkLock = lock;
+            lock.writeWaiting = true;
+            return lock;
+        });
+        try {
+            if (holder.stamp == 0) {
+                holder.stamp = holder.chunkLock.lock.writeLock();
+            }
+            return ReflectionUtils.compareAndSet(sections, expected, value, layer);
+        } finally {
+            chunks = FaweBukkitWorld.getWorldSendingChunksMap(worldName);
+            chunks.computeIfPresent(pair, (k, lock) -> {
+                if (lock != holder.chunkLock) {
+                    throw new IllegalStateException("SENDING_CHUNKS stored lock does not equal lock attempted to be unlocked?!");
+                }
+                lock.lock.unlockWrite(holder.stamp);
+                lock.writeWaiting = false;
+                // Keep the lock, etc. in the map as we're going to be accessing again later when sending
+                return lock;
+            });
+        }
+    }
+
+    /**
+     * Called before sending a chunk packet, filling the given stamp and stampedLock arrays' zeroth indices if the chunk packet
+     * send should go ahead.
+     * <p>
+     * Chunk packets should be sent if both of the following are met:
+     *  - There is no more than one current packet send ongoing
+     *  - There is no chunk section "write" waiting or ongoing,
+     * which are determined by the number of readers currently locking the StampedLock (i.e. the number of sends), if the
+     * stamped lock is currently write-locked and if the boolean for waiting write is true.
+     * <p>
+     * Utilises ConcurrentHashMap#compute for easy synchronisation
+     *
+     * @since TODO
+     */
+    protected static void beginChunkPacketSend(String worldName, IntPair pair, StampLockHolder stampedLock) {
+        ConcurrentHashMap<IntPair, ChunkSendLock> chunks = FaweBukkitWorld.getWorldSendingChunksMap(worldName);
+        chunks.compute(pair, (k, lock) -> {
+            if (lock == null) {
+                lock = new ChunkSendLock();
+            }
+            // Allow twice-read-locking, so if the packets have been created but not sent, we can queue another read
+            if (lock.writeWaiting || lock.lock.getReadLockCount() > 1 || lock.lock.isWriteLocked()) {
+                return lock;
+            }
+            stampedLock.stamp = lock.lock.readLock();
+            stampedLock.chunkLock = lock;
+            return lock;
+        });
+    }
+
+    /**
+     * Releases the read lock acquired when sending a chunk packet for a chunk
+     *
+     * @since TODO
+     */
+    protected static void endChunkPacketSend(String worldName, IntPair pair, StampLockHolder lockHolder) {
+        ConcurrentHashMap<IntPair, ChunkSendLock> chunks = FaweBukkitWorld.getWorldSendingChunksMap(worldName);
+        chunks.computeIfPresent(pair, (k, lock) -> {
+            if (lock.lock != lockHolder.chunkLock.lock) {
+                throw new IllegalStateException("SENDING_CHUNKS stored lock does not equal lock attempted to be unlocked?!");
+            }
+            lock.lock.unlockRead(lockHolder.stamp);
+            // Do not continue to store the lock if we may not need it (i.e. chunk has been sent, may not be sent again)
+            return null;
+        });
+    }
+
+    public static final class StampLockHolder {
+        public long stamp;
+        public ChunkSendLock chunkLock = null;
+    }
+
+    public static final class ChunkSendLock {
+
+        public final StampedLock lock = new StampedLock();
+        public boolean writeWaiting = false;
+
+    }
+
 }

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/BukkitWorld.java

@@ -118,9 +118,9 @@ public class BukkitWorld extends AbstractWorld {
         HAS_MIN_Y = temp;
     }
 
-    private WeakReference<World> worldRef;
+    protected WeakReference<World> worldRef;
     //FAWE start
-    private final String worldNameRef;
+    protected final String worldNameRef;
     //FAWE end
     private final WorldNativeAccess<?, ?, ?> worldNativeAccess;
 

worldedit-core/src/main/java/com/fastasyncworldedit/core/math/IntPair.java

@@ -4,7 +4,9 @@ public record IntPair(int x, int z) {
 
     @Override
     public int hashCode() {
-        return (x << 16) | (z & 0xFFFF);
+        int i = 1664525 * x + 1013904223;
+        int j = 1664525 * (z ^ -559038737) + 1013904223;
+        return i ^ j;
     }
 
     @Override