From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 23 May 2020 17:03:41 -0400
Subject: [PATCH] Optimize sending packets to nearby locations (sounds/effects)

Instead of using the entire world or player list, use the distance
maps to only iterate players who are even seeing the chunk the packet
is originating from.

This will drastically cut down on packet sending cost for worlds with
lots of players in them.

diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
index 9b726de6daeba42120f3a948fbdcf080d0e72917..269580ae2a6edca979ccc1e46df144468ea70a18 100644
--- a/src/main/java/net/minecraft/server/PlayerList.java
+++ b/src/main/java/net/minecraft/server/PlayerList.java
@@ -1027,11 +1027,27 @@ public abstract class PlayerList {
             world = (WorldServer) entityhuman.world;
         }
 
-        List<? extends EntityHuman> players1 = world == null ? players : world.players;
-        for (int j = 0; j < players1.size(); ++j) {
-            EntityHuman entity = players1.get(j);
-            if (!(entity instanceof EntityPlayer)) continue;
-            EntityPlayer entityplayer = (EntityPlayer) entity;
+        // Paper start
+        if (world == null && dimensionmanager != null) {
+            world = dimensionmanager.world;
+        }
+        if (world == null) {
+            LOGGER.error("Sending packet to invalid world" + entityhuman + " " + dimensionmanager + " - " + packet.getClass().getName(), new Throwable());
+            return; // ??? shouldn't happen...
+        }
+        ChunkProviderServer chunkProvider = (ChunkProviderServer) world.chunkProvider;
+        if (chunkProvider == null) {
+            // ??? Shouldn't be possible but seem some hacky plugins apparently do hack things.
+            return;
+        }
+        com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<EntityPlayer> nearbyPlayers = chunkProvider.playerChunkMap.playerViewDistanceBroadcastMap.getObjectsInRange(MCUtil.fastFloor(d0) >> 4, MCUtil.fastFloor(d2) >> 4);
+        if (nearbyPlayers == null) {
+            return;
+        }
+        Object[] backingSet = nearbyPlayers.getBackingSet();
+        for (Object object : backingSet) {
+            if (!(object instanceof EntityPlayer)) continue;
+            EntityPlayer entityplayer = (EntityPlayer) object;
             // Paper end
 
             // CraftBukkit start - Test if player receiving packet can see the source of the packet