From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Samsuik <kfian294ma4@gmail.com>
Date: Mon, 2 Dec 2024 21:46:31 +0000
Subject: [PATCH] Improve paper biome cache locking


diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
index bfe9dc935c87e01fb435d8b46ce413b84ca74856..526c7f4ae3388f5dbb5661f1be04ebb46f533f30 100644
--- a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+++ b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
@@ -366,13 +366,29 @@ public class CraftBlock implements Block {
         return (biome == null) ? Biome.CUSTOM : biome;
     }
 
-    private static final java.util.Map<org.bukkit.block.Biome, net.minecraft.resources.ResourceKey<net.minecraft.world.level.biome.Biome>> BIOME_KEY_CACHE = Collections.synchronizedMap(new java.util.EnumMap<>(Biome.class)); // Paper
+    // Sakura start - improve paper biome cache locking
+    private static final java.util.Map<org.bukkit.block.Biome, net.minecraft.resources.ResourceKey<net.minecraft.world.level.biome.Biome>> BIOME_KEY_CACHE = new java.util.EnumMap<>(Biome.class); // Paper
+    private static final java.util.concurrent.locks.StampedLock BIOME_KEY_CACHE_LOCK = new java.util.concurrent.locks.StampedLock();
     public static Holder<net.minecraft.world.level.biome.Biome> biomeToBiomeBase(net.minecraft.core.Registry<net.minecraft.world.level.biome.Biome> registry, Biome bio) {
         if (bio == null || bio == Biome.CUSTOM) {
             return null;
         }
 
-        return registry.getHolderOrThrow(BIOME_KEY_CACHE.computeIfAbsent(bio, b -> ResourceKey.create(net.minecraft.core.Registry.BIOME_REGISTRY, CraftNamespacedKey.toMinecraft(b.getKey())))); // Paper - cache key
+        // NOTE: Could get rid of the map by splitting up this patch and storing a reference in Biome (under api)
+        long stamp = BIOME_KEY_CACHE_LOCK.tryOptimisticRead();
+        ResourceKey<net.minecraft.world.level.biome.Biome> biomeKey = null;
+        try {
+            biomeKey = BIOME_KEY_CACHE.get(bio);
+        } catch (Exception ignored) {
+            // precaution
+        }
+        if (biomeKey == null || !BIOME_KEY_CACHE_LOCK.validate(stamp)) {
+            stamp = BIOME_KEY_CACHE_LOCK.writeLock();
+            biomeKey = BIOME_KEY_CACHE.computeIfAbsent(bio, b -> ResourceKey.create(net.minecraft.core.Registry.BIOME_REGISTRY, CraftNamespacedKey.toMinecraft(b.getKey()))); // Paper - cache key
+            BIOME_KEY_CACHE_LOCK.unlockWrite(stamp);
+        }
+        return registry.getHolderOrThrow(biomeKey);
+        // Sakura end - improve paper biome cache locking
     }
 
     @Override