S21/S26 packet static buffer thread safety

Author: FalsePattern

src/main/java/com/falsepattern/chunk/internal/mixin/helpers/LockHelper.java

@@ -0,0 +1,30 @@
+/*
+ * ChunkAPI
+ *
+ * Copyright (C) 2023-2025 FalsePattern, The MEGA Team, LegacyModdingMC contributors
+ * All Rights Reserved
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, only version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.falsepattern.chunk.internal.mixin.helpers;
+
+import java.util.concurrent.locks.ReentrantLock;
+
+public class LockHelper {
+    public static final ReentrantLock bufferLockS21PacketChunkData = new ReentrantLock();
+    public static final ReentrantLock bufferLockS26PacketMapChunkBulk = new ReentrantLock();
+}

src/main/java/com/falsepattern/chunk/internal/mixin/mixins/common/vanilla/S21PacketChunkDataMixin.java

@@ -23,6 +23,7 @@
 package com.falsepattern.chunk.internal.mixin.mixins.common.vanilla;
 
 import com.falsepattern.chunk.internal.DataRegistryImpl;
+import com.falsepattern.chunk.internal.mixin.helpers.LockHelper;
 import lombok.val;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Overwrite;
@@ -90,10 +91,6 @@ public static S21PacketChunkData.Extracted func_149269_a(Chunk chunk, boolean fo
         ExtendedBlockStorage[] subChunks = chunk.getBlockStorageArray();
         S21PacketChunkData.Extracted extracted = new S21PacketChunkData.Extracted();
 
-        if (buffer.length < DataRegistryImpl.maxPacketSize()) {
-            buffer = new byte[DataRegistryImpl.maxPacketSize()];
-        }
-
         if (forceUpdate) {
             chunk.sendUpdates = true;
         }
@@ -104,10 +101,21 @@ public static S21PacketChunkData.Extracted func_149269_a(Chunk chunk, boolean fo
             }
         }
 
-        int length = DataRegistryImpl.writeToBuffer(chunk, extracted.field_150280_b, forceUpdate, buffer);
+        while (!LockHelper.bufferLockS21PacketChunkData.tryLock()) {
+            Thread.yield();
+        }
+        try {
+            if (buffer.length < DataRegistryImpl.maxPacketSize()) {
+                buffer = new byte[DataRegistryImpl.maxPacketSize()];
+            }
+
+            int length = DataRegistryImpl.writeToBuffer(chunk, extracted.field_150280_b, forceUpdate, buffer);
 
-        extracted.field_150282_a = new byte[length];
-        System.arraycopy(buffer, 0, extracted.field_150282_a, 0, length);
+            extracted.field_150282_a = new byte[length];
+            System.arraycopy(buffer, 0, extracted.field_150282_a, 0, length);
+        } finally {
+            LockHelper.bufferLockS21PacketChunkData.unlock();
+        }
         return extracted;
     }
 

src/main/java/com/falsepattern/chunk/internal/mixin/mixins/common/vanilla/S26PacketMapChunkBulkMixin.java

@@ -22,6 +22,7 @@
 
 package com.falsepattern.chunk.internal.mixin.mixins.common.vanilla;
 
+import com.falsepattern.chunk.internal.mixin.helpers.LockHelper;
 import lombok.val;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Overwrite;
@@ -90,21 +91,29 @@ public void readPacketData(PacketBuffer data) throws IOException {
         subChunkMSBMasks = new int[chunkCount];
         datas = new byte[chunkCount][];
 
-        if (inflaterBuffer.length < deflatedSize) {
-            inflaterBuffer = new byte[deflatedSize];
+        while (!LockHelper.bufferLockS26PacketMapChunkBulk.tryLock()) {
+            Thread.yield();
         }
-
-        data.readBytes(inflaterBuffer, 0, deflatedSize);
-        byte[] buf = new byte[S21PacketChunkData.func_149275_c() * chunkCount];
-        Inflater inflater = new Inflater();
-        inflater.setInput(inflaterBuffer, 0, deflatedSize);
-
+        byte[] buf;
         try {
-            inflater.inflate(buf);
-        } catch (DataFormatException dataformatexception) {
-            throw new IOException("Bad compressed data format");
+            if (inflaterBuffer.length < deflatedSize) {
+                inflaterBuffer = new byte[deflatedSize];
+            }
+
+            data.readBytes(inflaterBuffer, 0, deflatedSize);
+            buf = new byte[S21PacketChunkData.func_149275_c() * chunkCount];
+            Inflater inflater = new Inflater();
+            inflater.setInput(inflaterBuffer, 0, deflatedSize);
+
+            try {
+                inflater.inflate(buf);
+            } catch (DataFormatException dataformatexception) {
+                throw new IOException("Bad compressed data format");
+            } finally {
+                inflater.end();
+            }
         } finally {
-            inflater.end();
+            LockHelper.bufferLockS26PacketMapChunkBulk.unlock();
         }
 
         int pos = 0;