Paper/nms-patches/PlayerChunkMap.patch

--- a/net/minecraft/server/PlayerChunkMap.java
+++ b/net/minecraft/server/PlayerChunkMap.java
@@ -7,17 +7,26 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
+// CraftBukkit start
+import java.util.Collections;
+import java.util.Queue;
+import java.util.LinkedList;
+import org.bukkit.craftbukkit.chunkio.ChunkIOExecutor;
+import java.util.HashMap;
+// CraftBukkit end
+
 public class PlayerChunkMap {
 
     private static final Logger a = LogManager.getLogger();
     private final WorldServer world;
     private final List<EntityPlayer> managedPlayers = Lists.newArrayList();
     private final LongHashMap<PlayerChunkMap.PlayerChunk> d = new LongHashMap();
-    private final List<PlayerChunkMap.PlayerChunk> e = Lists.newArrayList();
-    private final List<PlayerChunkMap.PlayerChunk> f = Lists.newArrayList();
+    private final Queue<PlayerChunkMap.PlayerChunk> e = new java.util.concurrent.ConcurrentLinkedQueue<PlayerChunkMap.PlayerChunk>(); // CraftBukkit ArrayList -> ConcurrentLinkedQueue
+    private final Queue<PlayerChunkMap.PlayerChunk> f = new java.util.concurrent.ConcurrentLinkedQueue<PlayerChunkMap.PlayerChunk>(); // CraftBukkit ArrayList -> ConcurrentLinkedQueue
     private int g;
     private long h;
     private final int[][] i = new int[][] { { 1, 0}, { 0, 1}, { -1, 0}, { 0, -1}};
+    private boolean wasNotEmpty; // CraftBukkit - add field
 
     public PlayerChunkMap(WorldServer worldserver) {
         this.world = worldserver;
@@ -36,26 +45,37 @@
         if (i - this.h > 8000L) {
             this.h = i;
 
-            for (j = 0; j < this.f.size(); ++j) {
-                playerchunkmap_playerchunk = (PlayerChunkMap.PlayerChunk) this.f.get(j);
+            // CraftBukkit start - Use iterator
+            java.util.Iterator iterator = this.f.iterator();
+            while (iterator.hasNext()) {
+                playerchunkmap_playerchunk = (PlayerChunk) iterator.next();
                 playerchunkmap_playerchunk.b();
                 playerchunkmap_playerchunk.a();
             }
         } else {
-            for (j = 0; j < this.e.size(); ++j) {
-                playerchunkmap_playerchunk = (PlayerChunkMap.PlayerChunk) this.e.get(j);
+            java.util.Iterator iterator = this.e.iterator();
+            while (iterator.hasNext()) {
+                playerchunkmap_playerchunk = (PlayerChunk) iterator.next();
                 playerchunkmap_playerchunk.b();
+                iterator.remove();
+                // CraftBukkit end
             }
         }
 
-        this.e.clear();
+        // this.e.clear(); //CraftBukkit - Removals are already covered
         if (this.managedPlayers.isEmpty()) {
+            if (!wasNotEmpty) return; // CraftBukkit - Only do unload when we go from non-empty to empty
             WorldProvider worldprovider = this.world.worldProvider;
 
             if (!worldprovider.e()) {
                 this.world.chunkProviderServer.b();
             }
+            // CraftBukkit start
+            wasNotEmpty = false;
+        } else {
+            wasNotEmpty = true;
         }
+        // CraftBukkit end
 
     }
 
@@ -78,6 +98,16 @@
         return playerchunkmap_playerchunk;
     }
 
+    // CraftBukkit start - add method
+    public final boolean isChunkInUse(int x, int z) {
+        PlayerChunk pi = a(x, z, false);
+        if (pi != null) {
+            return (pi.b.size() > 0);
+        }
+        return false;
+    }
+    // CraftBukkit end
+
     public void flagDirty(BlockPosition blockposition) {
         int i = blockposition.getX() >> 4;
         int j = blockposition.getZ() >> 4;
@@ -96,11 +126,20 @@
         entityplayer.d = entityplayer.locX;
         entityplayer.e = entityplayer.locZ;
 
+        // CraftBukkit start - Load nearby chunks first
+        List<ChunkCoordIntPair> chunkList = new LinkedList<ChunkCoordIntPair>();
+
         for (int k = i - this.g; k <= i + this.g; ++k) {
             for (int l = j - this.g; l <= j + this.g; ++l) {
-                this.a(k, l, true).a(entityplayer);
+                chunkList.add(new ChunkCoordIntPair(k, l));
             }
         }
+        
+        Collections.sort(chunkList, new ChunkCoordComparator(entityplayer));
+        for (ChunkCoordIntPair pair : chunkList) {
+            this.a(pair.x, pair.z, true).a(entityplayer);
+        }
+        // CraftBukkit end
 
         this.managedPlayers.add(entityplayer);
         this.b(entityplayer);
@@ -188,12 +227,13 @@
             int i1 = this.g;
             int j1 = i - k;
             int k1 = j - l;
+            List<ChunkCoordIntPair> chunksToLoad = new LinkedList<ChunkCoordIntPair>(); // CraftBukkit
 
             if (j1 != 0 || k1 != 0) {
                 for (int l1 = i - i1; l1 <= i + i1; ++l1) {
                     for (int i2 = j - i1; i2 <= j + i1; ++i2) {
                         if (!this.a(l1, i2, k, l, i1)) {
-                            this.a(l1, i2, true).a(entityplayer);
+                            chunksToLoad.add(new ChunkCoordIntPair(l1, i2)); // CraftBukkit
                         }
 
                         if (!this.a(l1 - j1, i2 - k1, i, j, i1)) {
@@ -209,6 +249,17 @@
                 this.b(entityplayer);
                 entityplayer.d = entityplayer.locX;
                 entityplayer.e = entityplayer.locZ;
+
+                // CraftBukkit start - send nearest chunks first
+                Collections.sort(chunksToLoad, new ChunkCoordComparator(entityplayer));
+                for (ChunkCoordIntPair pair : chunksToLoad) {
+                    this.a(pair.x, pair.z, true).a(entityplayer);
+                }
+
+                if (j1 > 1 || j1 < -1 || k1 > 1 || k1 < -1) {
+                    Collections.sort(entityplayer.chunkCoordIntPairQueue, new ChunkCoordComparator(entityplayer));
+                }
+                // CraftBukkit end
             }
         }
     }
@@ -271,12 +322,22 @@
         private int f;
         private long g;
 
+        // CraftBukkit start - add fields
+        private final HashMap<EntityPlayer, Runnable> players = new HashMap<EntityPlayer, Runnable>();
+        private boolean loaded = false;
+        private Runnable loadedRunnable = new Runnable() {
+            public void run() {
+                PlayerChunk.this.loaded = true;
+            }
+        };
+        // CraftBukkit end
+
         public PlayerChunk(int i, int j) {
             this.location = new ChunkCoordIntPair(i, j);
-            PlayerChunkMap.this.a().chunkProviderServer.getChunkAt(i, j);
+            PlayerChunkMap.this.a().chunkProviderServer.getChunkAt(i, j, loadedRunnable); // CraftBukkit
         }
 
-        public void a(EntityPlayer entityplayer) {
+        public void a(final EntityPlayer entityplayer) {  // CraftBukkit - added final to argument
             if (this.b.contains(entityplayer)) {
                 PlayerChunkMap.a.debug("Failed to add player. {} already is in chunk {}, {}", new Object[] { entityplayer, Integer.valueOf(this.location.x), Integer.valueOf(this.location.z)});
             } else {
@@ -285,18 +346,50 @@
                 }
 
                 this.b.add(entityplayer);
-                entityplayer.chunkCoordIntPairQueue.add(this.location);
+                // CraftBukkit start - use async chunk io
+                Runnable playerRunnable;
+                if (this.loaded) {
+                    playerRunnable = null;
+                    entityplayer.chunkCoordIntPairQueue.add(this.location);
+                } else {
+                    playerRunnable = new Runnable() {
+                        public void run() {
+                            entityplayer.chunkCoordIntPairQueue.add(PlayerChunk.this.location);
+                        }
+                    };
+                    PlayerChunkMap.this.a().chunkProviderServer.getChunkAt(this.location.x, this.location.z, playerRunnable);
+                }
+
+                this.players.put(entityplayer, playerRunnable);
+                // CraftBukkit end
             }
         }
 
         public void b(EntityPlayer entityplayer) {
             if (this.b.contains(entityplayer)) {
+                // CraftBukkit start - If we haven't loaded yet don't load the chunk just so we can clean it up
+                if (!this.loaded) {
+                    ChunkIOExecutor.dropQueuedChunkLoad(PlayerChunkMap.this.a(), this.location.x, this.location.z, this.players.get(entityplayer));
+                    this.b.remove(entityplayer);
+                    this.players.remove(entityplayer);
+
+                    if (this.b.isEmpty()) {
+                        ChunkIOExecutor.dropQueuedChunkLoad(PlayerChunkMap.this.a(), this.location.x, this.location.z, this.loadedRunnable);
+                        long i = (long) this.location.x + 2147483647L | (long) this.location.z + 2147483647L << 32;
+                        PlayerChunkMap.this.d.remove(i);
+                        PlayerChunkMap.this.f.remove(this);
+                    }
+
+                    return;
+                }
+                // CraftBukkit end
                 Chunk chunk = PlayerChunkMap.this.world.getChunkAt(this.location.x, this.location.z);
 
                 if (chunk.isReady()) {
                     entityplayer.playerConnection.sendPacket(new PacketPlayOutMapChunk(chunk, true, 0));
                 }
 
+                this.players.remove(entityplayer); // CraftBukkit
                 this.b.remove(entityplayer);
                 entityplayer.chunkCoordIntPairQueue.remove(this.location);
                 if (this.b.isEmpty()) {
@@ -421,4 +514,47 @@
 
         }
     }
+
+    // CraftBukkit start - Sorter to load nearby chunks first
+    private static class ChunkCoordComparator implements java.util.Comparator<ChunkCoordIntPair> {
+        private int x;
+        private int z;
+
+        public ChunkCoordComparator (EntityPlayer entityplayer) {
+            x = (int) entityplayer.locX >> 4;
+            z = (int) entityplayer.locZ >> 4;
+        }
+
+        public int compare(ChunkCoordIntPair a, ChunkCoordIntPair b) {
+            if (a.equals(b)) {
+                return 0;
+            }
+
+            // Subtract current position to set center point
+            int ax = a.x - this.x;
+            int az = a.z - this.z;
+            int bx = b.x - this.x;
+            int bz = b.z - this.z;
+
+            int result = ((ax - bx) * (ax + bx)) + ((az - bz) * (az + bz));
+            if (result != 0) {
+                return result;
+            }
+
+            if (ax < 0) {
+                if (bx < 0) {
+                    return bz - az;
+                } else {
+                    return -1;
+                }
+            } else {
+                if (bx < 0) {
+                    return 1;
+                } else {
+                    return az - bz;
+                }
+            }
+        }
+    }
+    // CraftBukkit end
 }