From 6ca61f000f507833bd90db76a36dd4f920c63d87 Mon Sep 17 00:00:00 2001
From: SquidDev <bonzoweb@hotmail.co.uk>
Date: Mon, 16 Apr 2018 15:30:44 +0100
Subject: [PATCH] Minor performance improvements to WiredNetworkChange

This should improve the performance of the common case, where one
peripheral set is empty.
---
 .../shared/wired/WiredNetworkChange.java      | 20 +++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/main/java/dan200/computercraft/shared/wired/WiredNetworkChange.java b/src/main/java/dan200/computercraft/shared/wired/WiredNetworkChange.java
index 4b53d24da..8cc20683d 100644
--- a/src/main/java/dan200/computercraft/shared/wired/WiredNetworkChange.java
+++ b/src/main/java/dan200/computercraft/shared/wired/WiredNetworkChange.java
@@ -10,6 +10,8 @@ import java.util.Map;
 
 public class WiredNetworkChange implements IWiredNetworkChange
 {
+    private static final WiredNetworkChange EMPTY = new WiredNetworkChange( Collections.emptyMap(), Collections.emptyMap() );
+
     private final Map<String, IPeripheral> removed;
     private final Map<String, IPeripheral> added;
 
@@ -26,16 +28,30 @@ public class WiredNetworkChange implements IWiredNetworkChange
 
     public static WiredNetworkChange added( Map<String, IPeripheral> added )
     {
-        return new WiredNetworkChange( Collections.emptyMap(), Collections.unmodifiableMap( added ) );
+        return added.isEmpty() ? EMPTY : new WiredNetworkChange( Collections.emptyMap(), Collections.unmodifiableMap( added ) );
     }
 
     public static WiredNetworkChange removed( Map<String, IPeripheral> removed )
     {
-        return new WiredNetworkChange( Collections.unmodifiableMap( removed ), Collections.emptyMap() );
+        return removed.isEmpty() ? EMPTY : new WiredNetworkChange( Collections.unmodifiableMap( removed ), Collections.emptyMap() );
     }
 
     public static WiredNetworkChange changeOf( Map<String, IPeripheral> oldPeripherals, Map<String, IPeripheral> newPeripherals )
     {
+        // Handle the trivial cases, where all peripherals have been added or removed.
+        if( oldPeripherals.isEmpty() && newPeripherals.isEmpty() )
+        {
+            return EMPTY;
+        }
+        else if( oldPeripherals.isEmpty() )
+        {
+            return new WiredNetworkChange( Collections.emptyMap(), newPeripherals );
+        }
+        else if( newPeripherals.isEmpty() )
+        {
+            return new WiredNetworkChange( oldPeripherals, Collections.emptyMap() );
+        }
+
         Map<String, IPeripheral> added = new HashMap<>( newPeripherals );
         Map<String, IPeripheral> removed = new HashMap<>();