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/players/PlayerList.java b/src/main/java/net/minecraft/server/players/PlayerList.java
index 6b23b9389ff92ae8016d4adb289ac2a097670be5..f5334be5d9c799da16198ecb0f69f17a2bf4a1eb 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -1137,16 +1137,40 @@ public abstract class PlayerList {
     }
 
     public void broadcast(@Nullable net.minecraft.world.entity.player.Player player, double x, double y, double z, double distance, ResourceKey<Level> worldKey, Packet<?> packet) {
-        for (int i = 0; i < this.players.size(); ++i) {
-            ServerPlayer entityplayer = (ServerPlayer) this.players.get(i);
+        ServerLevel world = null;
+        if (player != null && player.level instanceof ServerLevel) {
+            world = (ServerLevel) player.level;
+        }
 
-            // CraftBukkit start - Test if player receiving packet can see the source of the packet
-            if (player != null && player instanceof ServerPlayer && !entityplayer.getBukkitEntity().canSee(((ServerPlayer) player).getBukkitEntity())) {
-               continue;
+        // Paper start
+        if (world == null) {
+            world = server.getLevel(worldKey);
+        }
+        net.minecraft.server.level.ChunkMap chunkMap = world != null ? world.getChunkSource().chunkMap : null;
+        Object[] backingSet;
+        if (chunkMap == null) {
+            // Really shouldn't happen...
+            backingSet = world != null ? world.players.toArray() : players.toArray();
+        } else {
+            com.destroystokyo.paper.util.misc.PooledLinkedHashSets.PooledObjectLinkedOpenHashSet<ServerPlayer> nearbyPlayers = chunkMap.playerViewDistanceBroadcastMap.getObjectsInRange(MCUtil.fastFloor(x) >> 4, MCUtil.fastFloor(z) >> 4);
+            if (nearbyPlayers == null) {
+                return;
             }
+            backingSet = nearbyPlayers.getBackingSet();
+        }
+
+        for (Object object : backingSet) {
+            if (!(object instanceof ServerPlayer)) continue;
+            ServerPlayer entityplayer = (ServerPlayer) object;
+            // Paper end
+
+            // CraftBukkit start - Test if player receiving packet can see the source of the packet
+            //if (entityhuman != null && entityhuman instanceof EntityPlayer && !entityplayer.getBukkitEntity().canSee(((EntityPlayer) entityhuman).getBukkitEntity())) { // Paper
+               //continue; // Paper
+            //} // Paper
             // CraftBukkit end
 
-            if (entityplayer != player && entityplayer.level.dimension() == worldKey) {
+            if (entityplayer != player && entityplayer.level.dimension() == worldKey && (!(player instanceof ServerPlayer) || entityplayer.getBukkitEntity().canSee(((ServerPlayer) player).getBukkitEntity()))) { // Paper
                 double d4 = x - entityplayer.getX();
                 double d5 = y - entityplayer.getY();
                 double d6 = z - entityplayer.getZ();