From 094c4c043fd86f6d9c1ab8feb1a1910fb58c9f9b Mon Sep 17 00:00:00 2001
From: CraftBukkit/Spigot <noreply+git-craftbukkit@papermc.io>
Date: Sun, 20 Feb 2011 23:22:28 +0100
Subject: [PATCH] Second part of NPE and arctan update :3

By: VictorD <victor.danell@gmail.com>
---
 .../org/bukkit/craftbukkit/CraftChunk.java    | 31 ++++++++++++-------
 .../org/bukkit/craftbukkit/CraftWorld.java    |  5 ++-
 .../java/org/bukkit/craftbukkit/TrigMath.java |  3 +-
 3 files changed, 24 insertions(+), 15 deletions(-)

diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/CraftChunk.java b/paper-server/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
index 592e12033e..c9469f5d21 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/CraftChunk.java
@@ -1,6 +1,7 @@
 
 package org.bukkit.craftbukkit;
 
+import java.lang.ref.WeakReference;
 import java.util.HashMap;
 
 import net.minecraft.server.WorldServer;
@@ -11,27 +12,38 @@ import org.bukkit.block.Block;
 import org.bukkit.craftbukkit.block.CraftBlock;
 
 public class CraftChunk implements Chunk {
-    private net.minecraft.server.Chunk chunk;
+    private WeakReference<net.minecraft.server.Chunk> weakChunk;
     private final HashMap<Integer, Block> cache = new HashMap<Integer, Block>();
-
+    private WorldServer worldServer;
+    private int x;
+    private int z;
+    
     public CraftChunk(net.minecraft.server.Chunk chunk) {
-        this.chunk = chunk;
+        this.weakChunk = new WeakReference<net.minecraft.server.Chunk>(chunk);
+        worldServer = (WorldServer) getHandle().d;
+        x = getHandle().j;
+        z = getHandle().k;
     }
 
     public World getWorld() {
-        return ((WorldServer) chunk.d).getWorld();
+        return worldServer.getWorld();
     }
 
     public net.minecraft.server.Chunk getHandle() {
-        return chunk;
+        net.minecraft.server.Chunk c = weakChunk.get();
+        if (c == null) {
+            weakChunk = new WeakReference<net.minecraft.server.Chunk>(worldServer.c(x,z));
+            c = weakChunk.get();
+        }
+        return c;
     }
 
     public int getX() {
-        return chunk.j;
+        return x;
     }
 
     public int getZ() {
-        return chunk.k;
+        return z;
     }
 
     @Override
@@ -48,8 +60,5 @@ public class CraftChunk implements Chunk {
         }
         return block;
     }
-
-    public void breakLink() {
-        this.chunk = null;
-    }
 }
+
diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java b/paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
index 2f3fe70563..aca525176d 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java
@@ -47,12 +47,11 @@ public class CraftWorld implements World {
     }
 
     public void preserveChunk( CraftChunk chunk ) {
-        chunk.breakLink();
-        unloadedChunks.put( chunk.getX() << 16 + chunk.getZ(), chunk );
+        unloadedChunks.put( (chunk.getX() << 16) + chunk.getZ(), chunk );
     }
 
     public CraftChunk popPreservedChunk( int x, int z ) {
-        return unloadedChunks.remove( x << 16 + z );
+        return unloadedChunks.remove( (x << 16) + z );
     }
 
     public Block getBlockAt(int x, int y, int z) {
diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/TrigMath.java b/paper-server/src/main/java/org/bukkit/craftbukkit/TrigMath.java
index 0d207b37da..2a623bf0f7 100644
--- a/paper-server/src/main/java/org/bukkit/craftbukkit/TrigMath.java
+++ b/paper-server/src/main/java/org/bukkit/craftbukkit/TrigMath.java
@@ -1,6 +1,7 @@
 package org.bukkit.craftbukkit;
 /**
- * Got this code from a post by user aioobe on stackoverflow.com
+ * Credits for this class goes to user aioobe on stackoverflow.com
+ * Source: http://stackoverflow.com/questions/4454630/j2me-calculate-the-the-distance-between-2-latitude-and-longitude
  *
  */
 public class TrigMath {