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 c4242a1602bbb02541c330bc02016f15c8644358..7eb3088d47ff78198e01a3a12b0ce6abe9d6ca6b 100644
--- a/src/main/java/net/minecraft/server/players/PlayerList.java
+++ b/src/main/java/net/minecraft/server/players/PlayerList.java
@@ -1129,16 +1129,40 @@ 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();