Entity: cache id

This workarounds ANOTHER stupid stdlib bug. While entities are ticking SOMETIMES the lock *of the sync* is not releases after acquiring the read lock and no other threads can acquire the lock. I debugged this and it is a race condition in the ReentrantReadWriteLock (or in the synchronizer) class. Pretty ironic.

src/main/java/de/bixilon/minosoft/data/entities/entities/Entity.kt

@@ -55,10 +55,20 @@ abstract class Entity(
 ) : Initializable, EntityAttachable {
     private var flags: Int by data(FLAGS_DATA, 0x00) { it.toInt() }
     protected val random = Random()
+    var _id: Int? = null
+    var _uuid: UUID? = null
     val id: Int?
-        get() = session.world.entities.getId(this)
+        get() {
+            if (_id != null) return _id
+            _id = session.world.entities.getId(this)
+            return _id
+        }
     open val uuid: UUID?
-        get() = session.world.entities.getUUID(this)
+        get() {
+            if (_uuid != null) return _uuid
+            _uuid = session.world.entities.getUUID(this)
+            return _uuid
+        }
 
     @Deprecated(message = "Use session.version", replaceWith = ReplaceWith("session.version.versionId"))
     protected val versionId: Int get() = session.version.versionId
@@ -95,6 +105,7 @@ abstract class Entity(
 
     open val canRaycast: Boolean get() = true
 
+
     var age = 0
         private set
 

src/main/java/de/bixilon/minosoft/data/world/entities/WorldEntities.kt

@@ -96,6 +96,8 @@ class WorldEntities : Iterable<Entity> {
 
     fun remove(entity: Entity) {
         lock.lock()
+        entity._id = null
+        entity._uuid = null
         if (entity !is LocalPlayerEntity && !entities.remove(entity)) {
             lock.unlock()
             return
@@ -112,6 +114,8 @@ class WorldEntities : Iterable<Entity> {
             lock.unlock()
             return
         }
+        entity._id = null
+        entity._uuid = null
         if (entity is LocalPlayerEntity) {
             idEntityMap.put(entityId, entity)
             lock.unlock()
@@ -192,6 +196,8 @@ class WorldEntities : Iterable<Entity> {
     fun clear(session: PlaySession, local: Boolean = false) {
         this.lock.lock()
         for (entity in this.entities) {
+            entity._id = null
+            entity._uuid = null
             if (!local && entity is LocalPlayerEntity) continue
             entityIdMap.remove(entity)?.let { idEntityMap.remove(it) }
             entityUUIDMap.remove(entity)?.let { uuidEntityMap.remove(it) }

src/main/java/de/bixilon/minosoft/protocol/packets/s2c/play/entity/spawn/EntityObjectSpawnS2CP.kt

@@ -1,6 +1,6 @@
 /*
  * Minosoft
- * Copyright (C) 2020-2024 Moritz Zwerger
+ * Copyright (C) 2020-2025 Moritz Zwerger
  *
  * This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
  *
@@ -62,11 +62,11 @@ class EntityObjectSpawnS2CP(buffer: PlayInByteBuffer) : PlayS2CPacket {
         }
         entity.startInit()
         entity.setObjectData(data)
+        velocity?.let { entity.physics.velocity = it }
     }
 
     override fun handle(session: PlaySession) {
         session.world.entities.add(entityId, entityUUID, entity)
-        velocity?.let { entity.physics.velocity = it }
     }
 
     override fun log(reducedLog: Boolean) {