From b55e5b8da41d8a876be04bb1181a2a83054e44b7 Mon Sep 17 00:00:00 2001
From: Xekep <Xekep@users.noreply.github.com>
Date: Thu, 26 Feb 2026 20:29:53 +0300
Subject: [PATCH 1/2] Optimize handler dispatch with copy-on-write snapshots

Avoid per-invocation list allocations and lock holding in HandlerList.Invoke by using a snapshot array refreshed on register/unregister.
---
 TShockAPI/HandlerList.cs | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/TShockAPI/HandlerList.cs b/TShockAPI/HandlerList.cs
index a258d99be..983c2fc59 100644
--- a/TShockAPI/HandlerList.cs
+++ b/TShockAPI/HandlerList.cs
@@ -37,6 +37,7 @@ public class HandlerItem
 
 		protected object HandlerLock = new object();
 		protected List<HandlerItem> Handlers { get; set; }
+		private HandlerItem[] HandlerSnapshot { get; set; } = Array.Empty<HandlerItem>();
 		public HandlerList()
 		{
 			Handlers = new List<HandlerItem>();
@@ -59,6 +60,7 @@ public void Register(HandlerItem obj)
 			{
 				Handlers.Add(obj);
 				Handlers = Handlers.OrderBy(h => (int)h.Priority).ToList();
+				HandlerSnapshot = Handlers.ToArray();
 			}
 		}
 
@@ -66,21 +68,21 @@ public void UnRegister(EventHandler<T> handler)
 		{
 			lock (HandlerLock)
 			{
-				Handlers.RemoveAll(h => h.Handler.Equals(handler));
+				if (Handlers.RemoveAll(h => h.Handler.Equals(handler)) > 0)
+				{
+					HandlerSnapshot = Handlers.ToArray();
+				}
 			}
 		}
 
 		public void Invoke(object sender, T e)
 		{
-			List<HandlerItem> handlers;
-			lock (HandlerLock)
-			{
-				//Copy the list for invoking as to not keep it locked during the invokes
-				handlers = new List<HandlerItem>(Handlers);
-			}
+			var handlers = HandlerSnapshot;
+			if (handlers.Length == 0)
+				return;
 
 			var hargs = e as HandledEventArgs;
-			for (int i = 0; i < handlers.Count; i++)
+			for (int i = 0; i < handlers.Length; i++)
 			{
 				if (hargs == null || !hargs.Handled || (hargs.Handled && handlers[i].GetHandled))
 				{

From 1736b23f2b222ee8e603027ad04d229b0de10753 Mon Sep 17 00:00:00 2001
From: Xekep <Xekep@users.noreply.github.com>
Date: Fri, 27 Feb 2026 06:00:30 +0300
Subject: [PATCH 2/2] Fix handler snapshot publication visibility

---
 TShockAPI/HandlerList.cs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/TShockAPI/HandlerList.cs b/TShockAPI/HandlerList.cs
index 983c2fc59..3222414e3 100644
--- a/TShockAPI/HandlerList.cs
+++ b/TShockAPI/HandlerList.cs
@@ -20,6 +20,7 @@ You should have received a copy of the GNU General Public License
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
+using System.Threading;
 
 namespace TShockAPI
 {
@@ -37,7 +38,7 @@ public class HandlerItem
 
 		protected object HandlerLock = new object();
 		protected List<HandlerItem> Handlers { get; set; }
-		private HandlerItem[] HandlerSnapshot { get; set; } = Array.Empty<HandlerItem>();
+		private HandlerItem[] _handlerSnapshot = Array.Empty<HandlerItem>();
 		public HandlerList()
 		{
 			Handlers = new List<HandlerItem>();
@@ -60,7 +61,7 @@ public void Register(HandlerItem obj)
 			{
 				Handlers.Add(obj);
 				Handlers = Handlers.OrderBy(h => (int)h.Priority).ToList();
-				HandlerSnapshot = Handlers.ToArray();
+				Volatile.Write(ref _handlerSnapshot, Handlers.ToArray());
 			}
 		}
 
@@ -70,14 +71,14 @@ public void UnRegister(EventHandler<T> handler)
 			{
 				if (Handlers.RemoveAll(h => h.Handler.Equals(handler)) > 0)
 				{
-					HandlerSnapshot = Handlers.ToArray();
+					Volatile.Write(ref _handlerSnapshot, Handlers.ToArray());
 				}
 			}
 		}
 
 		public void Invoke(object sender, T e)
 		{
-			var handlers = HandlerSnapshot;
+			var handlers = Volatile.Read(ref _handlerSnapshot);
 			if (handlers.Length == 0)
 				return;