Added CachedObject to access a single-object cache

src/main/java/net/minestom/server/instance/DynamicChunk.java

@@ -16,6 +16,7 @@ import net.minestom.server.utils.BlockPosition;
 import net.minestom.server.utils.binary.BinaryReader;
 import net.minestom.server.utils.binary.BinaryWriter;
 import net.minestom.server.utils.block.CustomBlockUtils;
+import net.minestom.server.utils.cache.CachedObject;
 import net.minestom.server.utils.callback.OptionalCallback;
 import net.minestom.server.utils.chunk.ChunkCallback;
 import net.minestom.server.utils.chunk.ChunkUtils;
@@ -26,7 +27,6 @@ import net.minestom.server.world.biomes.Biome;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.lang.ref.SoftReference;
 import java.util.Set;
 
 /**
@@ -60,8 +60,7 @@ public class DynamicChunk extends Chunk {
 
     private long lastChangeTime;
 
-    private SoftReference<ChunkDataPacket> cachedPacket = new SoftReference<>(null);
-    private long cachedPacketTime;
+    private CachedObject<ChunkDataPacket> cachedPacket = new CachedObject<>();
 
     public DynamicChunk(@NotNull Instance instance, @Nullable Biome[] biomes, int chunkX, int chunkZ,
                         @NotNull PaletteStorage blockPalette, @NotNull PaletteStorage customBlockPalette) {
@@ -387,22 +386,17 @@ public class DynamicChunk extends Chunk {
     @NotNull
     @Override
     protected ChunkDataPacket createFreshPacket() {
-        ChunkDataPacket packet = cachedPacket.get();
-        if (packet != null && cachedPacketTime == getLastChangeTime()) {
-            return packet;
-        }
-        packet = new ChunkDataPacket(getIdentifier(), getLastChangeTime());
-        packet.biomes = biomes;
-        packet.chunkX = chunkX;
-        packet.chunkZ = chunkZ;
-        packet.paletteStorage = blockPalette.clone();
-        packet.customBlockPaletteStorage = customBlockPalette.clone();
-        packet.blockEntities = blockEntities.clone();
-        packet.blocksData = blocksData.clone();
-
-        this.cachedPacketTime = getLastChangeTime();
-        this.cachedPacket = new SoftReference<>(packet);
-        return packet;
+        return cachedPacket.getUpdatedCache(() -> {
+            ChunkDataPacket chunkDataPacket = new ChunkDataPacket(getIdentifier(), getLastChangeTime());
+            chunkDataPacket.biomes = biomes;
+            chunkDataPacket.chunkX = chunkX;
+            chunkDataPacket.chunkZ = chunkZ;
+            chunkDataPacket.paletteStorage = blockPalette.clone();
+            chunkDataPacket.customBlockPaletteStorage = customBlockPalette.clone();
+            chunkDataPacket.blockEntities = blockEntities.clone();
+            chunkDataPacket.blocksData = blocksData.clone();
+            return chunkDataPacket;
+        }, getLastChangeTime());
     }
 
     @NotNull

src/main/java/net/minestom/server/item/ItemMeta.java

@@ -6,6 +6,7 @@ import net.minestom.server.instance.block.Block;
 import net.minestom.server.item.attribute.ItemAttribute;
 import net.minestom.server.utils.binary.BinaryWriter;
 import net.minestom.server.utils.binary.Writeable;
+import net.minestom.server.utils.cache.CachedObject;
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -33,8 +34,8 @@ public class ItemMeta implements Writeable {
     private final NBTCompound nbt;
     private final ItemMetaBuilder emptyBuilder;
 
-    private String cachedSNBT;
-    private ByteBuf cachedBuffer;
+    private CachedObject<String> cachedSNBT = new CachedObject<>();
+    private CachedObject<ByteBuf> cachedBuffer = new CachedObject<>();
 
     protected ItemMeta(@NotNull ItemMetaBuilder metaBuilder) {
         this.damage = metaBuilder.damage;
@@ -128,10 +129,7 @@ public class ItemMeta implements Writeable {
     }
 
     public @NotNull String toSNBT() {
-        if (cachedSNBT == null) {
-            this.cachedSNBT = nbt.toSNBT();
-        }
-        return cachedSNBT;
+        return cachedSNBT.getCache(nbt::toSNBT);
     }
 
     @Override
@@ -155,12 +153,12 @@ public class ItemMeta implements Writeable {
 
     @Override
     public synchronized void write(@NotNull BinaryWriter writer) {
-        if (cachedBuffer == null) {
+        final var buffer = cachedBuffer.getCache(() -> {
             BinaryWriter w = new BinaryWriter();
             w.writeNBT("", nbt);
-            this.cachedBuffer = w.getBuffer();
-        }
-        writer.write(cachedBuffer);
-        this.cachedBuffer.resetReaderIndex();
+            return w.getBuffer();
+        });
+        writer.write(buffer);
+        buffer.resetReaderIndex();
     }
 }

src/main/java/net/minestom/server/utils/cache/CachedObject.java

@@ -0,0 +1,69 @@
+package net.minestom.server.utils.cache;
+
+import com.google.common.annotations.Beta;
+import org.jetbrains.annotations.NotNull;
+
+import java.lang.ref.SoftReference;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Supplier;
+
+/**
+ * Represents a single that can be collected by the garbage collector
+ * depending on memory demand.
+ *
+ * @param <T> the object to cache
+ */
+@Beta
+public class CachedObject<T> extends SoftReference<AtomicReference<T>> {
+
+    private long cacheTime;
+
+    public CachedObject() {
+        super(new AtomicReference<>());
+    }
+
+    /**
+     * Retrieves the cache.
+     *
+     * @param supplier supplier for the value if absent
+     * @return the cache
+     */
+    public @NotNull T getCache(@NotNull Supplier<@NotNull T> supplier) {
+        var referent = get();
+        assert referent != null;
+        var value = referent.get();
+        if (value == null) {
+            value = supplier.get();
+            referent.set(value);
+        }
+        return value;
+    }
+
+    /**
+     * Retrieves the cache, and ensure that the value is up-to-date.
+     *
+     * @param supplier   supplier for the value if absent or outdated
+     * @param lastUpdate the required internal timestamp, supplier will be called otherwise
+     * @return the cache
+     */
+    public @NotNull T getUpdatedCache(@NotNull Supplier<@NotNull T> supplier, long lastUpdate) {
+        var referent = get();
+        assert referent != null;
+        var value = referent.get();
+        if (value == null || cacheTime != lastUpdate) {
+            value = supplier.get();
+            this.cacheTime = lastUpdate;
+            referent.set(value);
+        }
+        return value;
+    }
+
+    /**
+     * @deprecated use {@link #getCache(Supplier)}
+     */
+    @Override
+    @Deprecated
+    public AtomicReference<T> get() {
+        return super.get();
+    }
+}