Merge branch 'master' into gh-pages

ProtocolLib/src/com/comphenix/protocol/AsynchronousManager.java

@@ -0,0 +1,78 @@
+package com.comphenix.protocol;
+
+import java.util.Set;
+import java.util.logging.Logger;
+
+import org.bukkit.plugin.Plugin;
+
+import com.comphenix.protocol.async.AsyncListenerHandler;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.events.PacketListener;
+
+/**
+ * Represents a asynchronous packet handler.
+ * 
+ * @author Kristian
+ */
+public interface AsynchronousManager {
+
+	/**
+	 * Registers an asynchronous packet handler.
+	 * <p>
+	 * To start listening asynchronously, pass the getListenerLoop() runnable to a different thread.
+	 * @param plugin - the plugin that is registering the handler.
+	 * @param listener - the packet listener that will recieve these asynchronous events.
+	 * @return An asynchrouns handler.
+	 */
+	public abstract AsyncListenerHandler registerAsyncHandler(PacketListener listener);
+
+	/**
+	 * Unregisters and closes the given asynchronous handler.
+	 * @param handler - asynchronous handler.
+	 */
+	public abstract void unregisterAsyncHandler(AsyncListenerHandler handler);
+
+	/**
+	 * Unregisters every asynchronous handler associated with this plugin.
+	 * @param plugin - the original plugin.
+	 */
+	public void unregisterAsyncHandlers(Plugin plugin);
+	
+	/**
+	 * Retrieves a immutable set containing the ID of the sent server packets that will be 
+	 * observed by the asynchronous listeners.
+	 * @return Every filtered server packet.
+	 */
+	public abstract Set<Integer> getSendingFilters();
+
+	/**
+	 * Retrieves a immutable set containing the ID of the recieved client packets that will be
+	 * observed by the asynchronous listeners.
+	 * @return Every filtered client packet.
+	 */
+	public abstract Set<Integer> getReceivingFilters();
+
+	/**
+	 * Determine if a given synchronous packet has asynchronous listeners.
+	 * @param packet - packet to test.
+	 * @return TRUE if it does, FALSE otherwise.
+	 */
+	public abstract boolean hasAsynchronousListeners(PacketEvent packet);
+
+	/**
+	 * Retrieve the default packet stream.
+	 * @return Default packet stream.
+	 */
+	public abstract PacketStream getPacketStream();
+
+	/**
+	 * Retrieve the default error logger.
+	 * @return Default logger.
+	 */
+	public abstract Logger getLogger();
+
+	/**
+	 * Remove listeners, close threads and transmit every delayed packet.
+	 */
+	public abstract void cleanupAll();
+}

ProtocolLib/src/com/comphenix/protocol/PacketStream.java

@@ -0,0 +1,55 @@
+package com.comphenix.protocol;
+
+import java.lang.reflect.InvocationTargetException;
+
+import org.bukkit.entity.Player;
+
+import com.comphenix.protocol.events.PacketContainer;
+
+/**
+ * Represents a object capable of sending or receiving packets.
+ * 
+ * @author Kristian
+ */
+public interface PacketStream {
+	
+	/**
+	 * Send a packet to the given player.
+	 * @param reciever - the reciever.
+	 * @param packet - packet to send.
+	 * @throws InvocationTargetException - if an error occured when sending the packet.
+	 */
+	public void sendServerPacket(Player reciever, PacketContainer packet) 
+			throws InvocationTargetException;
+
+	/**
+	 * Send a packet to the given player.
+	 * @param reciever - the reciever.
+	 * @param packet - packet to send.
+	 * @param filters - whether or not to invoke any packet filters.
+	 * @throws InvocationTargetException - if an error occured when sending the packet.
+	 */
+	public void sendServerPacket(Player reciever, PacketContainer packet, boolean filters)
+			throws InvocationTargetException;
+
+	/**
+	 * Simulate recieving a certain packet from a given player.
+	 * @param sender - the sender.
+	 * @param packet - the packet that was sent.
+	 * @throws InvocationTargetException If the reflection machinery failed.
+	 * @throws IllegalAccessException If the underlying method caused an error.
+	 */
+	public void recieveClientPacket(Player sender, PacketContainer packet) 
+			throws IllegalAccessException, InvocationTargetException;
+
+	/**
+	 * Simulate recieving a certain packet from a given player.
+	 * @param sender - the sender.
+	 * @param packet - the packet that was sent.
+	 * @param filters - whether or not to invoke any packet filters.
+	 * @throws InvocationTargetException If the reflection machinery failed.
+	 * @throws IllegalAccessException If the underlying method caused an error.
+	 */
+	public void recieveClientPacket(Player sender, PacketContainer packet, boolean filters)
+			throws IllegalAccessException, InvocationTargetException;
+}

ProtocolLib/src/com/comphenix/protocol/ProtocolLibrary.java

@@ -25,8 +25,10 @@ import org.bukkit.Server;
 import org.bukkit.plugin.PluginManager;
 import org.bukkit.plugin.java.JavaPlugin;
 
+import com.comphenix.protocol.async.AsyncFilterManager;
 import com.comphenix.protocol.injector.PacketFilterManager;
 import com.comphenix.protocol.metrics.Statistics;
+import com.comphenix.protocol.reflect.compiler.BackgroundCompiler;
 
 public class ProtocolLibrary extends JavaPlugin {
 	
@@ -39,10 +41,19 @@ public class ProtocolLibrary extends JavaPlugin {
 	// Metrics and statistisc
 	private Statistics statistisc;
 	
+	// Structure compiler
+	private BackgroundCompiler backgroundCompiler;
+	
+	// Used to clean up server packets that have expired. 
+	// But mostly required to simulate recieving client packets.
+	private int asyncPacketTask = -1;
+	private int tickCounter = 0;
+	private static final int ASYNC_PACKET_DELAY = 1;
+	
 	@Override
 	public void onLoad() {
 		logger = getLoggerSafely();
-		protocolManager = new PacketFilterManager(getClassLoader(), logger);
+		protocolManager = new PacketFilterManager(getClassLoader(), getServer(), logger);
 	}
 	
 	@Override
@@ -50,6 +61,12 @@ public class ProtocolLibrary extends JavaPlugin {
 		Server server = getServer();
 		PluginManager manager = server.getPluginManager();
 		
+		// Initialize background compiler
+		if (backgroundCompiler == null) {
+			backgroundCompiler = new BackgroundCompiler(getClassLoader());
+			BackgroundCompiler.setInstance(backgroundCompiler);
+		}
+
 		// Notify server managers of incompatible plugins
 		checkForIncompatibility(manager);
 		
@@ -59,6 +76,9 @@ public class ProtocolLibrary extends JavaPlugin {
 		// Inject our hook into already existing players
 		protocolManager.initializePlayers(server.getOnlinePlayers());
 		
+		// Timeout
+		createAsyncTask(server);
+		
 		// Try to enable statistics
 		try {
 			statistisc = new Statistics(this);
@@ -69,9 +89,32 @@ public class ProtocolLibrary extends JavaPlugin {
 		}
 	}
 	
+	private void createAsyncTask(Server server) {
+		try {
+			if (asyncPacketTask >= 0)
+				throw new IllegalStateException("Async task has already been created");
+			
+			// Attempt to create task
+			asyncPacketTask = server.getScheduler().scheduleSyncRepeatingTask(this, new Runnable() {
+				@Override
+				public void run() {
+					AsyncFilterManager manager = (AsyncFilterManager) protocolManager.getAsynchronousManager();
+					
+					// We KNOW we're on the main thread at the moment
+					manager.sendProcessedPackets(tickCounter++, true);
+				}
+			}, ASYNC_PACKET_DELAY, ASYNC_PACKET_DELAY);
+		
+		} catch (Throwable e) {
+			if (asyncPacketTask == -1) {
+				logger.log(Level.SEVERE, "Unable to create packet timeout task.", e);
+			}
+		}
+	}
+	
 	private void checkForIncompatibility(PluginManager manager) {
 		// Plugin authors: Notify me to remove these
-		String[] incompatiblePlugins = { "TagAPI" };
+		String[] incompatiblePlugins = {};
 		
 		for (String plugin : incompatiblePlugins) {
 			if (manager.getPlugin(plugin) != null) {
@@ -83,6 +126,19 @@ public class ProtocolLibrary extends JavaPlugin {
 	
 	@Override
 	public void onDisable() {
+		// Disable compiler
+		if (backgroundCompiler != null) {
+			backgroundCompiler.shutdownAll();
+			backgroundCompiler = null;
+			BackgroundCompiler.setInstance(null);
+		}
+		
+		// Clean up
+		if (asyncPacketTask >= 0) {
+			getServer().getScheduler().cancelTask(asyncPacketTask);
+			asyncPacketTask = -1;
+		}
+		
 		protocolManager.close();
 		protocolManager = null;
 		statistisc = null;

ProtocolLib/src/com/comphenix/protocol/ProtocolManager.java

@@ -17,7 +17,6 @@
 
 package com.comphenix.protocol;
 
-import java.lang.reflect.InvocationTargetException;
 import java.util.List;
 import java.util.Set;
 
@@ -35,7 +34,7 @@ import com.google.common.collect.ImmutableSet;
  * Represents an API for accessing the Minecraft protocol.
  * @author Kristian
  */
-public interface ProtocolManager {
+public interface ProtocolManager extends PacketStream {
 
 	/**
 	 * Retrieves a list of every registered packet listener.
@@ -66,46 +65,6 @@ public interface ProtocolManager {
 	 * @param plugin - the plugin to unload.
 	 */
 	public void removePacketListeners(Plugin plugin);
-	
-	/**
-	 * Send a packet to the given player.
-	 * @param reciever - the reciever.
-	 * @param packet - packet to send.
-	 * @throws InvocationTargetException - if an error occured when sending the packet.
-	 */
-	public void sendServerPacket(Player reciever, PacketContainer packet) 
-			throws InvocationTargetException;
-
-	/**
-	 * Send a packet to the given player.
-	 * @param reciever - the reciever.
-	 * @param packet - packet to send.
-	 * @param filters - whether or not to invoke any packet filters.
-	 * @throws InvocationTargetException - if an error occured when sending the packet.
-	 */
-	public void sendServerPacket(Player reciever, PacketContainer packet, boolean filters)
-			throws InvocationTargetException;
-
-	/**
-	 * Simulate recieving a certain packet from a given player.
-	 * @param sender - the sender.
-	 * @param packet - the packet that was sent.
-	 * @throws InvocationTargetException If the reflection machinery failed.
-	 * @throws IllegalAccessException If the underlying method caused an error.
-	 */
-	public void recieveClientPacket(Player sender, PacketContainer packet) 
-			throws IllegalAccessException, InvocationTargetException;
-
-	/**
-	 * Simulate recieving a certain packet from a given player.
-	 * @param sender - the sender.
-	 * @param packet - the packet that was sent.
-	 * @param filters - whether or not to invoke any packet filters.
-	 * @throws InvocationTargetException If the reflection machinery failed.
-	 * @throws IllegalAccessException If the underlying method caused an error.
-	 */
-	public void recieveClientPacket(Player sender, PacketContainer packet, boolean filters)
-			throws IllegalAccessException, InvocationTargetException;
 
 	/**
 	 * Constructs a new encapsulated Minecraft packet with the given ID.
@@ -163,4 +122,10 @@ public interface ProtocolManager {
 	 * @return TRUE if it has, FALSE otherwise.
 	 */
 	public boolean isClosed();
+
+	/**
+	 * Retrieve the current asyncronous packet manager.
+	 * @return Asyncronous packet manager.
+	 */
+	public AsynchronousManager getAsynchronousManager();
 }

ProtocolLib/src/com/comphenix/protocol/async/AsyncFilterManager.java

@@ -0,0 +1,301 @@
+package com.comphenix.protocol.async;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.logging.Logger;
+
+import org.bukkit.plugin.Plugin;
+import org.bukkit.scheduler.BukkitScheduler;
+
+import com.comphenix.protocol.AsynchronousManager;
+import com.comphenix.protocol.PacketStream;
+import com.comphenix.protocol.ProtocolManager;
+import com.comphenix.protocol.events.ListeningWhitelist;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.events.PacketListener;
+import com.comphenix.protocol.injector.PacketFilterManager;
+import com.comphenix.protocol.injector.PrioritizedListener;
+import com.google.common.base.Objects;
+
+/**
+ * Represents a filter manager for asynchronous packets.
+ * 
+ * @author Kristian
+ */
+public class AsyncFilterManager implements AsynchronousManager {
+
+	private PacketProcessingQueue serverProcessingQueue;
+	private PacketSendingQueue serverQueue;
+	
+	private PacketProcessingQueue clientProcessingQueue;
+	private PacketSendingQueue clientQueue;
+	
+	private Logger logger;
+	
+	// The likely main thread
+	private Thread mainThread;
+	
+	// Default scheduler
+	private BukkitScheduler scheduler;
+	
+	// Our protocol manager
+	private ProtocolManager manager;
+	
+	// Current packet index
+	private AtomicInteger currentSendingIndex = new AtomicInteger();
+	
+	// Whether or not we're currently cleaning up
+	private volatile boolean cleaningUp;
+	
+	public AsyncFilterManager(Logger logger, BukkitScheduler scheduler, ProtocolManager manager) {
+		
+		// Server packets are synchronized already
+		this.serverQueue = new PacketSendingQueue(false);
+		// Client packets must be synchronized
+		this.clientQueue = new PacketSendingQueue(true); 
+		
+		this.serverProcessingQueue = new PacketProcessingQueue(serverQueue);
+		this.clientProcessingQueue = new PacketProcessingQueue(clientQueue);
+		
+		this.scheduler = scheduler;
+		this.manager = manager;
+		
+		this.logger = logger;
+		this.mainThread = Thread.currentThread();
+	}
+	
+	@Override
+	public AsyncListenerHandler registerAsyncHandler(PacketListener listener) {
+		AsyncListenerHandler handler = new AsyncListenerHandler(mainThread, this, listener);
+		
+		ListeningWhitelist sendingWhitelist = listener.getSendingWhitelist();
+		ListeningWhitelist receivingWhitelist = listener.getReceivingWhitelist();
+		
+		// We need a synchronized listener to get the ball rolling
+		boolean hasListener = true;
+		
+		// Add listener to either or both processing queue
+		if (hasValidWhitelist(sendingWhitelist)) {
+			PacketFilterManager.verifyWhitelist(listener, sendingWhitelist);
+			serverProcessingQueue.addListener(handler, sendingWhitelist);
+			hasListener &= hasPacketListener(sendingWhitelist); 
+		}
+		
+		if (hasValidWhitelist(receivingWhitelist)) {
+			PacketFilterManager.verifyWhitelist(listener, receivingWhitelist);
+			clientProcessingQueue.addListener(handler, receivingWhitelist);
+			hasListener &= hasPacketListener(receivingWhitelist); 
+		}
+		
+		if (!hasListener) {
+			handler.setNullPacketListener(new NullPacketListener(listener));
+			manager.addPacketListener(handler.getNullPacketListener());
+		}
+		
+		return handler;
+	}
+	
+	/**
+	 * Determine if the given packets are represented.
+	 * @param whitelist - list of packets.
+	 * @return TRUE if they are all registered, FALSE otherwise.
+	 */
+	private boolean hasPacketListener(ListeningWhitelist whitelist) {
+		return manager.getSendingFilters().containsAll(whitelist.getWhitelist());
+	}
+	
+	private boolean hasValidWhitelist(ListeningWhitelist whitelist) {
+		return whitelist != null && whitelist.getWhitelist().size() > 0;
+	}
+	
+	@Override
+	public void unregisterAsyncHandler(AsyncListenerHandler handler) {
+		if (handler == null)
+			throw new IllegalArgumentException("listenerToken cannot be NULL");
+		
+		handler.cancel();	
+	}
+	
+	// Called by AsyncListenerHandler
+	void unregisterAsyncHandlerInternal(AsyncListenerHandler handler) {
+		
+		PacketListener listener = handler.getAsyncListener();
+		boolean synchronusOK = onMainThread();
+		
+		// Unregister null packet listeners
+		if (handler.getNullPacketListener() != null) {
+			manager.removePacketListener(handler.getNullPacketListener());
+		}
+		
+		// Just remove it from the queue(s)
+		if (hasValidWhitelist(listener.getSendingWhitelist())) {
+			List<Integer> removed = serverProcessingQueue.removeListener(handler, listener.getSendingWhitelist());
+			
+			// We're already taking care of this, so don't do anything
+			if (!cleaningUp)
+				serverQueue.signalPacketUpdate(removed, synchronusOK);
+		}
+		
+		if (hasValidWhitelist(listener.getReceivingWhitelist())) {
+			List<Integer> removed = clientProcessingQueue.removeListener(handler, listener.getReceivingWhitelist());
+			
+			if (!cleaningUp)
+				clientQueue.signalPacketUpdate(removed, synchronusOK);
+		}
+	}
+	
+	/**
+	 * Determine if we're running on the main thread.
+	 * @return TRUE if we are, FALSE otherwise.
+	 */
+	private boolean onMainThread() {
+		return Thread.currentThread().getId() == mainThread.getId();
+	}
+	
+	@Override
+	public void unregisterAsyncHandlers(Plugin plugin) {
+		unregisterAsyncHandlers(serverProcessingQueue, plugin);
+		unregisterAsyncHandlers(clientProcessingQueue, plugin);
+	}
+	
+	private void unregisterAsyncHandlers(PacketProcessingQueue processingQueue, Plugin plugin) {
+		
+		// Iterate through every packet listener
+		for (PrioritizedListener<AsyncListenerHandler> listener : processingQueue.values()) {			
+			// Remove the listener
+			if (Objects.equal(listener.getListener().getPlugin(), plugin)) {
+				unregisterAsyncHandler(listener.getListener());
+			}
+		}
+	}
+	
+	/**
+	 * Enqueue a packet for asynchronous processing.
+	 * @param syncPacket - synchronous packet event.
+	 * @param asyncMarker - the asynchronous marker to use.
+	 */
+	public void enqueueSyncPacket(PacketEvent syncPacket, AsyncMarker asyncMarker) {
+		PacketEvent newEvent = PacketEvent.fromSynchronous(syncPacket, asyncMarker);
+		
+		// Start the process
+		getSendingQueue(syncPacket).enqueue(newEvent);
+		
+		// We know this is occuring on the main thread, so pass TRUE
+		getProcessingQueue(syncPacket).enqueue(newEvent, true);
+	}
+	
+	@Override
+	public Set<Integer> getSendingFilters() {
+		return serverProcessingQueue.keySet();
+	}
+	
+	@Override
+	public Set<Integer> getReceivingFilters() {
+		return clientProcessingQueue.keySet();
+	}
+	
+	/**
+	 * Used to create a default asynchronous task.
+	 * @param plugin - the calling plugin.
+	 * @param runnable - the runnable.
+	 */
+	public void scheduleAsyncTask(Plugin plugin, Runnable runnable) {
+		scheduler.scheduleAsyncDelayedTask(plugin, runnable);
+	}
+	
+	@Override
+	public boolean hasAsynchronousListeners(PacketEvent packet) {
+		 Collection<?> list = getProcessingQueue(packet).getListener(packet.getPacketID());
+		 return list != null && list.size() > 0;
+	}
+	
+	/**
+	 * Construct a asynchronous marker with all the default values.
+	 * @return Asynchronous marker.
+	 */
+	public AsyncMarker createAsyncMarker() {
+		return createAsyncMarker(AsyncMarker.DEFAULT_SENDING_DELTA, AsyncMarker.DEFAULT_TIMEOUT_DELTA);
+	}
+	
+	/**
+	 * Construct an async marker with the given sending priority delta and timeout delta.
+	 * @param sendingDelta - how many packets we're willing to wait.
+	 * @param timeoutDelta - how long (in ms) until the packet expire.
+	 * @return An async marker.
+	 */
+	public AsyncMarker createAsyncMarker(long sendingDelta, long timeoutDelta) {
+		return createAsyncMarker(sendingDelta, timeoutDelta, 
+								 currentSendingIndex.incrementAndGet(), System.currentTimeMillis());
+	}
+	
+	// Helper method
+	private AsyncMarker createAsyncMarker(long sendingDelta, long timeoutDelta, long sendingIndex, long currentTime) {
+		return new AsyncMarker(manager, sendingIndex, sendingDelta, System.currentTimeMillis(), timeoutDelta);
+	}
+	
+	@Override
+	public PacketStream getPacketStream() {
+		return manager;
+	}
+
+	@Override
+	public Logger getLogger() {
+		return logger;
+	}
+
+	@Override
+	public void cleanupAll() {
+		cleaningUp = true;
+		serverProcessingQueue.cleanupAll();
+		serverQueue.cleanupAll();
+	}
+
+	/**
+	 * Signal that a packet is ready to be transmitted.
+	 * @param packet - packet to signal.
+	 */
+	public void signalPacketUpdate(PacketEvent packet) {
+		getSendingQueue(packet).signalPacketUpdate(packet, onMainThread());
+	}
+
+	/**
+	 * Retrieve the sending queue this packet belongs to.
+	 * @param packet - the packet.
+	 * @return The server or client sending queue the packet belongs to.
+	 */
+	private PacketSendingQueue getSendingQueue(PacketEvent packet) {
+		return packet.isServerPacket() ? serverQueue : clientQueue;
+	}
+	
+	/**
+	 * Signal that a packet has finished processing.
+	 * @param packet - packet to signal.
+	 */
+	public void signalProcessingDone(PacketEvent packet) {
+		getProcessingQueue(packet).signalProcessingDone();
+	}
+	
+	/**
+	 * Retrieve the processing queue this packet belongs to.
+	 * @param packet - the packet.
+	 * @return The server or client sending processing the packet belongs to.
+	 */
+	private PacketProcessingQueue getProcessingQueue(PacketEvent packet) {
+		return packet.isServerPacket() ? serverProcessingQueue : clientProcessingQueue;
+	}
+
+	/**
+	 * Send any due packets, or clean up packets that have expired.
+	 */
+	public void sendProcessedPackets(int tickCounter, boolean onMainThread) {
+		
+		// The server queue is unlikely to need checking that often
+		if (tickCounter % 10 == 0) {
+			serverQueue.trySendPackets(onMainThread);
+		}
+
+		clientQueue.trySendPackets(onMainThread);
+	}
+}

ProtocolLib/src/com/comphenix/protocol/async/AsyncListenerHandler.java

@@ -0,0 +1,210 @@
+package com.comphenix.protocol.async;
+
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.logging.Level;
+
+import org.bukkit.plugin.Plugin;
+
+import com.comphenix.protocol.events.PacketAdapter;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.events.PacketListener;
+
+/**
+ * Represents a handler for an asynchronous event.
+ * 
+ * @author Kristian
+ */
+public class AsyncListenerHandler {
+
+	/**
+	 * Signal an end to the packet processing.
+	 */
+	private static final PacketEvent INTERUPT_PACKET = new PacketEvent(new Object());
+	
+	// Default queue capacity
+	private static int DEFAULT_CAPACITY = 1024;
+	
+	// Cancel the async handler
+	private volatile boolean cancelled;
+	
+	// If we've started the listener loop before
+	private volatile boolean started;
+	
+	// The packet listener
+	private PacketListener listener;
+
+	// The filter manager
+	private AsyncFilterManager filterManager;
+	private NullPacketListener nullPacketListener;
+	
+	// List of queued packets
+	private ArrayBlockingQueue<PacketEvent> queuedPackets = new ArrayBlockingQueue<PacketEvent>(DEFAULT_CAPACITY);
+
+	// Minecraft main thread
+	private Thread mainThread;
+	
+	public AsyncListenerHandler(Thread mainThread, AsyncFilterManager filterManager, PacketListener listener) {
+		if (filterManager == null)
+			throw new IllegalArgumentException("filterManager cannot be NULL");
+		if (listener == null)
+			throw new IllegalArgumentException("listener cannot be NULL");
+
+		this.mainThread = mainThread;
+		this.filterManager = filterManager;
+		this.listener = listener;
+	}
+	
+	public boolean isCancelled() {
+		return cancelled;
+	}
+
+	public PacketListener getAsyncListener() {
+		return listener;
+	}
+
+	/**
+	 * Set the synchronized listener that has been automatically created.
+	 * @param nullPacketListener - automatically created listener.
+	 */
+	void setNullPacketListener(NullPacketListener nullPacketListener) {
+		this.nullPacketListener = nullPacketListener;
+	}
+
+	/**
+	 * Retrieve the synchronized listener that was automatically created.
+	 * @return Automatically created listener.
+	 */
+	PacketListener getNullPacketListener() {
+		return nullPacketListener;
+	}
+	
+	/**
+	 * Cancel the handler.
+	 */
+	public void cancel() {
+		// Remove the listener as quickly as possible
+		close();
+		
+		// Poison Pill Shutdown
+		queuedPackets.clear();
+		queuedPackets.add(INTERUPT_PACKET);
+	}
+	
+	/**
+	 * Queue a packet for processing.
+	 * @param packet - a packet for processing.
+	 * @throws IllegalStateException If the underlying packet queue is full.
+	 */
+	public void enqueuePacket(PacketEvent packet) {
+		if (packet == null)
+			throw new IllegalArgumentException("packet is NULL");
+		
+		queuedPackets.add(packet);
+	}
+	
+	/**
+	 * Create a runnable that will initiate the listener loop.
+	 * <p>
+	 * <b>Warning</b>: Never call the run() method in the main thread.
+	 */
+	public Runnable getListenerLoop() {
+		return new Runnable() {
+			@Override
+			public void run() {
+				listenerLoop();
+			}
+		};
+	}
+	
+	// DO NOT call this method from the main thread
+	private void listenerLoop() {
+		
+		// Danger, danger!
+		if (Thread.currentThread().getId() == mainThread.getId()) 
+			throw new IllegalStateException("Do not call this method from the main thread.");
+		if (started) 
+			throw new IllegalStateException("A listener cannot be run by multiple threads. Create a new listener instead.");
+		if (cancelled)
+			throw new IllegalStateException("Listener has been cancelled. Create a new listener instead.");
+		
+		// Proceed
+		started = true;
+		
+		try {
+			mainLoop:
+			while (!cancelled) {
+				PacketEvent packet = queuedPackets.take();
+				AsyncMarker marker = packet.getAsyncMarker();
+				
+				// Handle cancel requests
+				if (packet == null || marker == null || !packet.isAsynchronous()) {
+					break;
+				}
+				
+				// Here's the core of the asynchronous processing
+				try {
+					if (packet.isServerPacket())
+						listener.onPacketSending(packet);
+					else
+						listener.onPacketReceiving(packet);
+					
+				} catch (Throwable e) {
+					// Minecraft doesn't want your Exception.
+					filterManager.getLogger().log(Level.SEVERE, 
+							"Unhandled exception occured in onAsyncPacket() for " + getPluginName(), e);
+				}
+				
+				// Now, get the next non-cancelled listener
+				for (; marker.getListenerTraversal().hasNext(); ) {
+					AsyncListenerHandler handler = marker.getListenerTraversal().next().getListener();
+					
+					if (!handler.isCancelled()) {
+						handler.enqueuePacket(packet);
+						continue mainLoop;
+					}
+				}
+				
+				// There are no more listeners - queue the packet for transmission
+				filterManager.signalPacketUpdate(packet);
+				filterManager.signalProcessingDone(packet);
+			}
+			
+		} catch (InterruptedException e) {
+			// We're done
+		}
+		
+		// Clean up
+		close();
+	}
+	
+	private void close() {
+		// Remove the listener itself
+		if (!cancelled) {
+			filterManager.unregisterAsyncHandlerInternal(this);
+			cancelled = true;
+			started = false;
+		}
+	}
+	
+	private String getPluginName() {
+		return PacketAdapter.getPluginName(listener);
+	}
+
+	/**
+	 * Retrieve the plugin associated with this async listener.
+	 * @return The plugin.
+	 */
+	public Plugin getPlugin() {
+		return listener != null ? listener.getPlugin() : null;
+	}
+
+	/**
+	 * Start the asynchronous listener using the Bukkit scheduler.
+	 */
+	public void start() {
+		if (listener.getPlugin() == null)
+			throw new IllegalArgumentException("Cannot start task without a valid plugin.");
+		
+		filterManager.scheduleAsyncTask(listener.getPlugin(), getListenerLoop());
+	}
+}

ProtocolLib/src/com/comphenix/protocol/async/AsyncMarker.java

@@ -0,0 +1,305 @@
+package com.comphenix.protocol.async;
+
+import java.io.IOException;
+import java.io.Serializable;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Iterator;
+import java.util.List;
+
+import net.minecraft.server.Packet;
+
+import com.comphenix.protocol.PacketStream;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.injector.PrioritizedListener;
+import com.comphenix.protocol.reflect.FieldAccessException;
+import com.comphenix.protocol.reflect.FuzzyReflection;
+import com.google.common.primitives.Longs;
+
+/**
+ * Contains information about the packet that is being processed by asynchronous listeners.
+ * <p>
+ * Asynchronous listeners can use this to set packet timeout or transmission order.
+ * 
+ * @author Kristian
+ */
+public class AsyncMarker implements Serializable, Comparable<AsyncMarker> {
+		
+	/**
+	 * Generated by Eclipse.
+	 */
+	private static final long serialVersionUID = -2621498096616187384L;
+
+	/**
+	 * Default number of milliseconds until a packet will rejected.
+	 */
+	public static final int DEFAULT_TIMEOUT_DELTA = 60000;
+	
+	/**
+	 * Default number of packets to skip.
+	 */
+	public static final int DEFAULT_SENDING_DELTA = 0;
+	
+	/**
+	 * The packet stream responsible for transmitting the packet when it's done processing.
+	 */
+	private transient PacketStream packetStream;
+	
+	/**
+	 * Current list of async packet listeners.
+	 */
+	private transient Iterator<PrioritizedListener<AsyncListenerHandler>> listenerTraversal;
+	
+	// Timeout handling
+	private long initialTime;
+	private long timeout;
+	
+	// Packet order
+	private long originalSendingIndex;
+	private long newSendingIndex;
+	
+	// Whether or not the packet has been processed by the listeners
+	private volatile boolean processed;
+	
+	// Whether or not the packet has been sent
+	private volatile boolean transmitted;
+	
+	// Whether or not the asynchronous processing itself should be cancelled
+	private volatile boolean asyncCancelled;
+	
+	// Determine if Minecraft processes this packet asynchronously
+	private static Method isMinecraftAsync;
+	private static boolean alwaysSync;
+
+	/**
+	 * Create a container for asyncronous packets.
+	 * @param initialTime - the current time in milliseconds since 01.01.1970 00:00.
+	 */
+	AsyncMarker(PacketStream packetStream, long sendingIndex, long sendingDelta, long initialTime, long timeoutDelta) {
+		if (packetStream == null)
+			throw new IllegalArgumentException("packetStream cannot be NULL");
+		
+		this.packetStream = packetStream;
+		
+		// Timeout
+		this.initialTime = initialTime;
+		this.timeout = initialTime + timeoutDelta;
+		
+		// Sending index
+		this.originalSendingIndex = sendingIndex;
+		this.newSendingIndex = sendingIndex;
+	}
+	
+	/**
+	 * Retrieve the time the packet was initially queued for asynchronous processing.
+	 * @return The initial time in number of milliseconds since 01.01.1970 00:00. 
+	 */
+	public long getInitialTime() {
+		return initialTime;
+	}	
+
+	/**
+	 * Retrieve the time the packet will be forcefully rejected.
+	 * @return The time to reject the packet, in milliseconds since 01.01.1970 00:00.
+	 */
+	public long getTimeout() {
+		return timeout;
+	}
+	
+	/**
+	 * Set the time the packet will be forcefully rejected.
+	 * @param timeout - time to reject the packet, in milliseconds since 01.01.1970 00:00.
+	 */
+	public void setTimeout(long timeout) {
+		this.timeout = timeout;
+	}
+
+	/**
+	 * Retrieve the order the packet was originally transmitted.
+	 * @return The original packet index.
+	 */
+	public long getOriginalSendingIndex() {
+		return originalSendingIndex;
+	}
+
+	/**
+	 * Retrieve the desired sending order after processing has completed.
+	 * <p>
+	 * Higher sending order means lower priority.
+	 * @return Desired sending order.
+	 */
+	public long getNewSendingIndex() {
+		return newSendingIndex;
+	}
+
+	/**
+	 * Sets the desired sending order after processing has completed.
+	 * <p>
+	 * Higher sending order means lower priority.
+	 * @param newSendingIndex - new packet send index.
+	 */
+	public void setNewSendingIndex(long newSendingIndex) {
+		this.newSendingIndex = newSendingIndex;
+	}
+
+	/**
+	 * Retrieve the packet stream responsible for transmitting this packet.
+	 * @return The packet stream.
+	 */
+	public PacketStream getPacketStream() {
+		return packetStream;
+	}
+
+	/**
+	 * Sets the output packet stream responsible for transmitting this packet.
+	 * @param packetStream - new output packet stream.
+	 */
+	public void setPacketStream(PacketStream packetStream) {
+		this.packetStream = packetStream;
+	}
+
+	/**
+	 * Retrieve whether or not this packet has been processed by the async listeners.
+	 * @return TRUE if it has been processed, FALSE otherwise.
+	 */
+	public boolean isProcessed() {
+		return processed;
+	}
+
+	/**
+	 * Sets whether or not this packet has been processed by the async listeners.
+	 * @param processed - TRUE if it has, FALSE otherwise.
+	 */
+	void setProcessed(boolean processed) {
+		this.processed = processed;
+	}
+
+	/**
+	 * Retrieve whether or not this packet has already been sent.
+	 * @return TRUE if it has been sent before, FALSE otherwise.
+	 */
+	public boolean isTransmitted() {
+		return transmitted;
+	}
+
+	/**
+	 * Determine if this packet has expired.
+	 * @return TRUE if it has, FALSE otherwise.
+	 */
+	public boolean hasExpired() {
+		return hasExpired(System.currentTimeMillis());
+	}
+	
+	/**
+	 * Determine if this packet has expired given this time.
+	 * @param currentTime - the current time in milliseconds since 01.01.1970 00:00.
+	 * @return TRUE if it has, FALSE otherwise.
+	 */
+	public boolean hasExpired(long currentTime) {
+		return timeout < currentTime;
+	}
+	
+	/**
+	 * Determine if the asynchronous handling should be cancelled.
+	 * @return TRUE if it should, FALSE otherwise.
+	 */
+	public boolean isAsyncCancelled() {
+		return asyncCancelled;
+	}
+
+	/**
+	 * Set whether or not the asynchronous handling should be cancelled.
+	 * @param asyncCancelled - TRUE to cancel it, FALSE otherwise.
+	 */
+	public void setAsyncCancelled(boolean asyncCancelled) {
+		this.asyncCancelled = asyncCancelled;
+	}
+	
+	/**
+	 * Retrieve iterator for the next listener in line.
+	 * @return Next async packet listener iterator.
+	 */
+	public Iterator<PrioritizedListener<AsyncListenerHandler>> getListenerTraversal() {
+		return listenerTraversal;
+	}
+	
+	/**
+	 * Set the iterator for the next listener.
+	 * @param listenerTraversal - the new async packet listener iterator.
+	 */
+	void setListenerTraversal(Iterator<PrioritizedListener<AsyncListenerHandler>> listenerTraversal) {
+		this.listenerTraversal = listenerTraversal;
+	}
+	
+	/**
+	 * Transmit a given packet to the current packet stream.
+	 * @param event - the packet to send.
+	 * @throws IOException If the packet couldn't be sent.
+	 */
+	public void sendPacket(PacketEvent event) throws IOException {
+		try {
+			if (event.isServerPacket()) {
+				packetStream.sendServerPacket(event.getPlayer(), event.getPacket(), false);
+			} else {
+				packetStream.recieveClientPacket(event.getPlayer(), event.getPacket(), false);
+			}
+			transmitted = true;
+			
+		} catch (InvocationTargetException e) {
+			throw new IOException("Cannot send packet", e);
+		} catch (IllegalAccessException e) {
+			throw new IOException("Cannot send packet", e);
+		}
+	}
+	
+	/**
+	 * Determine if Minecraft allows asynchronous processing of this packet.
+	 * @return TRUE if it does, FALSE otherwise.
+	 */
+	public boolean isMinecraftAsync(PacketEvent event) throws FieldAccessException {
+		
+		if (isMinecraftAsync == null && !alwaysSync) {
+			try {
+				isMinecraftAsync = FuzzyReflection.fromClass(Packet.class).getMethodByName("a_.*");
+			} catch (RuntimeException e) {
+				// This will occur in 1.2.5 (or possibly in later versions)
+				List<Method> methods = FuzzyReflection.fromClass(Packet.class).
+										getMethodListByParameters(boolean.class, new Class[] {});
+				
+				// Try to look for boolean methods
+				if (methods.size() == 2) {
+					isMinecraftAsync = methods.get(1);
+				} else if (methods.size() == 1) {
+					// We're in 1.2.5
+					alwaysSync = true;
+				} else {
+					System.err.println("Cannot determine asynchronous state of packets!");
+					alwaysSync = true;
+				}
+			}
+		}
+		
+		if (alwaysSync) {
+			return false;
+		} else {
+			try {
+				// Wrap exceptions 
+				return (Boolean) isMinecraftAsync.invoke(event.getPacket().getHandle());
+			} catch (IllegalArgumentException e) {
+				throw new FieldAccessException("Illegal argument", e);
+			} catch (IllegalAccessException e) {
+				throw new FieldAccessException("Unable to reflect method call 'a_', or: isAsyncPacket.", e);
+			} catch (InvocationTargetException e) {
+				throw new FieldAccessException("Minecraft error", e);
+			}
+		}
+	}
+	
+	@Override
+	public int compareTo(AsyncMarker o) {
+		if (o == null)
+			return 1;
+		else
+			return Longs.compare(getNewSendingIndex(), o.getNewSendingIndex());
+	}
+}

ProtocolLib/src/com/comphenix/protocol/async/NullPacketListener.java

@@ -0,0 +1,62 @@
+package com.comphenix.protocol.async;
+
+import org.bukkit.plugin.Plugin;
+
+import com.comphenix.protocol.events.ListenerPriority;
+import com.comphenix.protocol.events.ListeningWhitelist;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.events.PacketListener;
+
+/**
+ * Represents a NO OPERATION listener.
+ * 
+ * @author Kristian
+ */
+class NullPacketListener implements PacketListener {
+	
+	private ListeningWhitelist sendingWhitelist;
+	private ListeningWhitelist receivingWhitelist;
+	private Plugin plugin;
+
+	/**
+	 * Create a no-op listener with the same whitelist and plugin as the given listener.
+	 * @param original - the packet listener to copy.
+	 */
+	public NullPacketListener(PacketListener original) {
+		this.sendingWhitelist = cloneWhitelist(ListenerPriority.LOW, original.getSendingWhitelist());
+		this.receivingWhitelist = cloneWhitelist(ListenerPriority.LOW, original.getReceivingWhitelist());
+		this.plugin = original.getPlugin();
+	}
+
+	@Override
+	public void onPacketSending(PacketEvent event) {
+		// NULL
+	}
+
+	@Override
+	public void onPacketReceiving(PacketEvent event) {
+		// NULL
+	}
+
+	@Override
+	public ListeningWhitelist getSendingWhitelist() {
+		return sendingWhitelist;
+	}
+
+	@Override
+	public ListeningWhitelist getReceivingWhitelist() {
+		return receivingWhitelist;
+	}
+	
+	private ListeningWhitelist cloneWhitelist(ListenerPriority priority, ListeningWhitelist whitelist) {
+		if (whitelist != null) 
+			return new ListeningWhitelist(priority, whitelist.getWhitelist());
+		else 
+			return null;
+	}
+
+	@Override
+	public Plugin getPlugin() {
+		return plugin;
+	}
+}

ProtocolLib/src/com/comphenix/protocol/async/PacketProcessingQueue.java

@@ -0,0 +1,133 @@
+package com.comphenix.protocol.async;
+
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.Semaphore;
+
+import com.comphenix.protocol.concurrency.AbstractConcurrentListenerMultimap;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.injector.PrioritizedListener;
+
+/**
+ * Handles the processing of every packet type.
+ * 
+ * @author Kristian
+ */
+class PacketProcessingQueue extends AbstractConcurrentListenerMultimap<AsyncListenerHandler> {
+
+	/**
+	 * Default maximum number of packets to process concurrently.
+	 */
+	public static final int DEFAULT_MAXIMUM_CONCURRENCY = 32;
+	
+	/**
+	 * Default maximum number of packets to queue for processing.
+	 */
+	public static final int DEFAULT_QUEUE_LIMIT = 1024 * 60;
+	
+	/**
+	 * Number of packets we're processing concurrently.
+	 */
+	private final int maximumConcurrency;
+	private Semaphore concurrentProcessing;
+	
+	// Queued packets for being processed
+	private ArrayBlockingQueue<PacketEvent> processingQueue;
+	
+	// Packets for sending
+	private PacketSendingQueue sendingQueue;
+
+	public PacketProcessingQueue(PacketSendingQueue sendingQueue) {
+		this(sendingQueue, DEFAULT_QUEUE_LIMIT, DEFAULT_MAXIMUM_CONCURRENCY);
+	}
+	
+	public PacketProcessingQueue(PacketSendingQueue sendingQueue, int queueLimit, int maximumConcurrency) {
+		super();
+		this.processingQueue = new ArrayBlockingQueue<PacketEvent>(queueLimit);
+		this.maximumConcurrency = maximumConcurrency;
+		this.concurrentProcessing = new Semaphore(maximumConcurrency);
+		this.sendingQueue = sendingQueue;
+	}
+	
+	/**
+	 * Enqueue a packet for processing by the asynchronous listeners.
+	 * @param packet - packet to process.
+	 * @param onMainThread - whether or not this is occuring on the main thread.
+	 * @return TRUE if we sucessfully queued the packet, FALSE if the queue ran out if space.
+	 */
+	public boolean enqueue(PacketEvent packet, boolean onMainThread) {
+		try {
+			processingQueue.add(packet);
+			
+			// Begin processing packets
+			signalBeginProcessing(onMainThread);
+			return true;
+		} catch (IllegalStateException e) {
+			return false;
+		}
+	}
+	
+	/**
+	 * Called by the current method and each thread to signal that a packet might be ready for processing.
+	 * @param onMainThread - whether or not this is occuring on the main thread.
+	 */
+	public void signalBeginProcessing(boolean onMainThread) {	
+		while (concurrentProcessing.tryAcquire()) {
+			PacketEvent packet = processingQueue.poll();
+			
+			// Any packet queued?
+			if (packet != null) {
+				Collection<PrioritizedListener<AsyncListenerHandler>> list = getListener(packet.getPacketID());
+				AsyncMarker marker = packet.getAsyncMarker();
+				
+				// Yes, removing the marker will cause the chain to stop
+				if (list != null) {
+					Iterator<PrioritizedListener<AsyncListenerHandler>> iterator = list.iterator();
+					
+					if (iterator.hasNext()) {
+						marker.setListenerTraversal(iterator);
+						iterator.next().getListener().enqueuePacket(packet);
+						continue;
+					}
+				}
+				
+				// The packet has no further listeners. Just send it.
+				sendingQueue.signalPacketUpdate(packet, onMainThread);
+				signalProcessingDone();
+				
+			} else {
+				// No more queued packets.
+				signalProcessingDone();
+				return;
+			}
+ 		}
+	}
+	
+	/**
+	 * Called when a packet has been processed.
+	 */
+	public void signalProcessingDone() {
+		concurrentProcessing.release();
+	}
+
+	/**
+	 * Retrieve the maximum number of packets to process at any given time.
+	 * @return Number of simultaneous packet to process.
+	 */
+	public int getMaximumConcurrency() {
+		return maximumConcurrency;
+	}
+	
+	public void cleanupAll() {
+		// Cancel all the threads and every listener
+		for (PrioritizedListener<AsyncListenerHandler> handler : values()) {
+			if (handler != null) {
+				handler.getListener().cancel();
+			}
+		}
+		
+		// Remove the rest, just in case
+		clearListeners();
+	}
+}

ProtocolLib/src/com/comphenix/protocol/async/PacketSendingQueue.java

@@ -0,0 +1,177 @@
+package com.comphenix.protocol.async;
+
+import java.io.IOException;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.PriorityBlockingQueue;
+
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.reflect.FieldAccessException;
+import com.google.common.collect.ComparisonChain;
+
+/**
+ * Represents packets ready to be transmitted to a client.
+ * @author Kristian
+ */
+class PacketSendingQueue {
+
+	private static final int INITIAL_CAPACITY = 64;
+	
+	private PriorityBlockingQueue<PacketEvent> sendingQueue;
+	
+	// Whether or not packet transmission can only occur on the main thread
+	private final boolean synchronizeMain;
+	
+	/**
+	 * Create a packet sending queue.
+	 * @param synchronizeMain - whether or not to synchronize with the main thread.
+	 */
+	public PacketSendingQueue(boolean synchronizeMain) {
+		this.synchronizeMain = synchronizeMain;
+		this.sendingQueue = new PriorityBlockingQueue<PacketEvent>(INITIAL_CAPACITY, new Comparator<PacketEvent>() {
+			// Compare using the async marker
+			@Override
+			public int compare(PacketEvent o1, PacketEvent o2) {
+				return ComparisonChain.start().
+					   compare(o1.getAsyncMarker(), o2.getAsyncMarker()).
+					   result();
+			}
+		});
+	}
+	
+	/**
+	 * Enqueue a packet for sending. 
+	 * @param packet
+	 */
+	public void enqueue(PacketEvent packet) {
+		sendingQueue.add(packet);
+	}
+	
+	/**
+	 * Invoked when one of the packets have finished processing.
+	 * @param packetUpdated - the packet that has now been updated.
+	 * @param onMainThread - whether or not this is occuring on the main thread.
+	 */
+	public synchronized void signalPacketUpdate(PacketEvent packetUpdated, boolean onMainThread) {
+		// Mark this packet as finished
+		packetUpdated.getAsyncMarker().setProcessed(true);
+		trySendPackets(onMainThread);
+	}
+
+	/***
+	 * Invoked when a list of packet IDs are no longer associated with any listeners.
+	 * @param packetsRemoved - packets that no longer have any listeners.
+	 * @param onMainThread - whether or not this is occuring on the main thread.
+	 */
+	public synchronized void signalPacketUpdate(List<Integer> packetsRemoved, boolean onMainThread) {
+		
+		Set<Integer> lookup = new HashSet<Integer>(packetsRemoved);
+		
+		// Note that this is O(n), so it might be expensive
+		for (PacketEvent event : sendingQueue) {
+			if (lookup.contains(event.getPacketID())) {
+				event.getAsyncMarker().setProcessed(true);
+			}
+		}
+		
+		// This is likely to have changed the situation a bit
+		trySendPackets(onMainThread);
+	}
+	
+	/**
+	 * Attempt to send any remaining packets.
+	 * @param onMainThread - whether or not this is occuring on the main thread.
+	 */
+	public void trySendPackets(boolean onMainThread) {
+				
+		// Transmit as many packets as we can
+		while (true) {
+			PacketEvent current = sendingQueue.peek();
+					
+			if (current != null) {
+				AsyncMarker marker = current.getAsyncMarker();
+				
+				// Abort if we're not on the main thread
+				if (synchronizeMain) {
+					try {
+						boolean wantAsync = marker.isMinecraftAsync(current);
+						boolean wantSync = !wantAsync;
+						
+						// Quit if we haven't fulfilled our promise
+						if ((onMainThread && wantAsync) || (!onMainThread && wantSync))
+							return;
+						
+					} catch (FieldAccessException e) {
+						e.printStackTrace();
+						return;
+					}
+				}
+				
+				if (marker.isProcessed() || marker.hasExpired()) {
+					if (marker.isProcessed() && !current.isCancelled()) {
+						sendPacket(current);
+					}
+					
+					sendingQueue.poll();
+					continue;
+				}
+			}
+			
+			// Only repeat when packets are removed
+			break;
+		}
+	}
+	
+	/**
+	 * Send every packet, regardless of the processing state.
+	 */
+	private void forceSend() {
+		while (true) {
+			PacketEvent current = sendingQueue.poll();
+			
+			if (current != null) {
+				sendPacket(current);
+			} else {
+				break;
+			}
+		}
+	}
+	
+	/**
+	 * Whether or not the packet transmission must synchronize with the main thread.
+	 * @return TRUE if it must, FALSE otherwise.
+	 */
+	public boolean isSynchronizeMain() {
+		return synchronizeMain;
+	}
+
+	/**
+	 * Transmit a packet, if it hasn't already.
+	 * @param event - the packet to transmit.
+	 */
+	private void sendPacket(PacketEvent event) {
+		
+		AsyncMarker marker = event.getAsyncMarker();
+		
+		try {
+			// Don't send a packet twice
+			if (marker != null && !marker.isTransmitted()) {
+				marker.sendPacket(event);
+			}
+			
+		} catch (IOException e) {
+			// Just print the error
+			e.printStackTrace();
+		}
+	}
+
+	/**
+	 * Automatically transmits every delayed packet.
+	 */
+	public void cleanupAll() {
+		// Note that the cleanup itself will always occur on the main thread
+		forceSend();
+	}
+}

ProtocolLib/src/com/comphenix/protocol/concurrency/AbstractConcurrentListenerMultimap.java

@@ -0,0 +1,131 @@
+package com.comphenix.protocol.concurrency;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+import com.comphenix.protocol.events.ListeningWhitelist;
+import com.comphenix.protocol.injector.PrioritizedListener;
+import com.google.common.collect.Iterables;
+
+/**
+ * A thread-safe implementation of a listener multimap.
+ * 
+ * @author Kristian
+ */
+public abstract class AbstractConcurrentListenerMultimap<TListener> {
+
+	// The core of our map
+	private ConcurrentMap<Integer, SortedCopyOnWriteArray<PrioritizedListener<TListener>>> listeners = 
+		new ConcurrentHashMap<Integer, SortedCopyOnWriteArray<PrioritizedListener<TListener>>>();
+	
+	/**
+	 * Adds a listener to its requested list of packet recievers.
+	 * @param listener - listener with a list of packets to recieve notifcations for.
+	 * @param whitelist - the packet whitelist to use.
+	 */
+	public void addListener(TListener listener, ListeningWhitelist whitelist) {
+		
+		PrioritizedListener<TListener> prioritized = new PrioritizedListener<TListener>(listener, whitelist.getPriority());
+		
+		for (Integer packetID : whitelist.getWhitelist()) {
+			addListener(packetID, prioritized);
+		}
+	}
+	
+	// Add the listener to a specific packet notifcation list
+	private void addListener(Integer packetID, PrioritizedListener<TListener> listener) {
+		
+		SortedCopyOnWriteArray<PrioritizedListener<TListener>> list = listeners.get(packetID);
+		
+		// We don't want to create this for every lookup
+		if (list == null) {
+			// It would be nice if we could use a PriorityBlockingQueue, but it doesn't preseve iterator order,
+			// which is a essential feature for our purposes.
+			final SortedCopyOnWriteArray<PrioritizedListener<TListener>> value = new SortedCopyOnWriteArray<PrioritizedListener<TListener>>();
+			
+			list = listeners.putIfAbsent(packetID, value);
+			
+			// We may end up creating multiple multisets, but we'll agree 
+			// on the one to use.
+			if (list == null) {
+				list = value;
+			}
+		}
+		
+		// Thread safe
+		list.add(listener);
+	}
+	
+	/**
+	 * Removes the given listener from the packet event list.
+	 * @param listener - listener to remove.
+	 * @param whitelist - the packet whitelist that was used.
+	 * @return Every packet ID that was removed due to no listeners.
+	 */
+	public List<Integer> removeListener(TListener listener, ListeningWhitelist whitelist) {
+	
+		List<Integer> removedPackets = new ArrayList<Integer>();
+		
+		// Again, not terribly efficient. But adding or removing listeners should be a rare event.
+		for (Integer packetID : whitelist.getWhitelist()) {
+			
+			SortedCopyOnWriteArray<PrioritizedListener<TListener>> list = listeners.get(packetID);
+			
+			// Remove any listeners
+			if (list != null) {
+				// Don't remove from newly created lists
+				if (list.size() > 0) {
+					// Remove this listener. Note that priority is generally ignored.
+					list.remove(new PrioritizedListener<TListener>(listener, whitelist.getPriority()));
+					
+					if (list.size() == 0) {
+						listeners.remove(packetID);
+						removedPackets.add(packetID);
+					}
+				}
+			}
+			
+			// Move on to the next
+		}
+		
+		return removedPackets;
+	}
+	
+	/**
+	 * Retrieve the registered listeners, in order from the lowest to the highest priority.
+	 * <p>
+	 * The returned list is thread-safe and doesn't require synchronization.
+	 * @param packetID - packet ID.
+	 * @return Registered listeners.
+	 */
+	public Collection<PrioritizedListener<TListener>> getListener(int packetID) {
+		return listeners.get(packetID);
+	}
+	
+	/**
+	 * Retrieve every listener.
+	 * @return Every listener.
+	 */
+	public Iterable<PrioritizedListener<TListener>> values() {
+		return Iterables.concat(listeners.values());
+	}
+	
+	/**
+	 * Retrieve every registered packet ID:
+	 * @return Registered packet ID.
+	 */
+	public Set<Integer> keySet() {
+		return listeners.keySet();
+	}
+	
+	/**
+	 * Remove all packet listeners.
+	 */
+	protected void clearListeners() {
+		listeners.clear();
+	}
+}

ProtocolLib/src/com/comphenix/protocol/events/ListeningWhitelist.java

@@ -62,7 +62,7 @@ public class ListeningWhitelist {
 	 * @return TRUE if there are any packets, FALSE otherwise.
 	 */
 	public boolean isEnabled() {
-		return whitelist != null || whitelist.size() > 0;
+		return whitelist != null && whitelist.size() > 0;
 	}
 	
 	/**
@@ -86,6 +86,23 @@ public class ListeningWhitelist {
 	    return Objects.hashCode(priority, whitelist);
 	}
 
+	/**
+	 * Determine if any of the given IDs can be found in the whitelist.
+	 * @param whitelist - whitelist to test.
+	 * @param idList - list of packet IDs to find. 
+	 * @return TRUE if any of the packets in the list can be found in the whitelist, FALSE otherwise.
+	 */
+	public static boolean containsAny(ListeningWhitelist whitelist, int... idList) {
+		if (whitelist != null) {
+			for (int i = 0; i < idList.length; i++) {
+				if (whitelist.getWhitelist().contains(idList[i]))
+					return true;
+			}
+		}
+		
+		return false;
+	}
+	
 	@Override
 	public boolean equals(final Object obj){
 	    if(obj instanceof ListeningWhitelist){

ProtocolLib/src/com/comphenix/protocol/events/PacketContainer.java

@@ -17,6 +17,12 @@
 
 package com.comphenix.protocol.events;
 
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
@@ -40,13 +46,18 @@ import net.minecraft.server.Packet;
  * 
  * @author Kristian
  */
-public class PacketContainer {
+public class PacketContainer implements Serializable {
 
-	protected Packet handle;
-	protected int id;
+	/**
+	 * Generated by Eclipse.
+	 */
+	private static final long serialVersionUID = 2074805748222377230L;
 	
+	protected int id;
+	protected transient Packet handle;
+
 	// Current structure modifier
-	protected StructureModifier<Object> structureModifier;
+	protected transient StructureModifier<Object> structureModifier;
 		
 	// Check whether or not certain classes exists
 	private static boolean hasWorldType = false;
@@ -54,6 +65,10 @@ public class PacketContainer {
 	// The getEntity method
 	private static Method getEntity;
 	
+	// Support for serialization
+	private static Method writeMethod;
+	private static Method readMethod;
+	
 	static {
 		try {
 			Class.forName("net.minecraft.server.WorldType");
@@ -291,4 +306,60 @@ public class PacketContainer {
 	public int getID() {
 		return id;
 	}
+	
+	private void writeObject(ObjectOutputStream output) throws IOException {
+	    // Default serialization 
+		output.defaultWriteObject();
+
+		// We'll take care of NULL packets as well
+		output.writeBoolean(handle != null);
+		
+		// Retrieve the write method by reflection
+		if (writeMethod == null)
+			writeMethod = FuzzyReflection.fromObject(handle).getMethodByParameters("write", DataOutputStream.class);
+		
+		try {
+			// Call the write-method
+			writeMethod.invoke(handle, new DataOutputStream(output));
+		} catch (IllegalArgumentException e) {
+			throw new IOException("Minecraft packet doesn't support DataOutputStream", e);
+		} catch (IllegalAccessException e) {
+			throw new RuntimeException("Insufficient security privileges.", e);
+		} catch (InvocationTargetException e) {
+			throw new IOException("Could not serialize Minecraft packet.", e);
+		}
+	}
+
+	private void readObject(ObjectInputStream input) throws ClassNotFoundException, IOException {
+	    // Default deserialization
+		input.defaultReadObject();
+		
+		// Get structure modifier
+		structureModifier = StructureCache.getStructure(id);
+
+	    // Don't read NULL packets
+	    if (input.readBoolean()) {
+	    	
+	    	// Create a default instance of the packet
+	    	handle = StructureCache.newPacket(id);
+	    	
+			// Retrieve the read method by reflection
+			if (readMethod == null)
+				readMethod = FuzzyReflection.fromObject(handle).getMethodByParameters("read", DataInputStream.class);
+	    	
+			// Call the read method
+			try {
+				readMethod.invoke(handle, new DataInputStream(input));
+			} catch (IllegalArgumentException e) {
+				throw new IOException("Minecraft packet doesn't support DataInputStream", e);
+			} catch (IllegalAccessException e) {
+				throw new RuntimeException("Insufficient security privileges.", e);
+			} catch (InvocationTargetException e) {
+				throw new IOException("Could not deserialize Minecraft packet.", e);
+			}
+			
+			// And we're done
+			structureModifier = structureModifier.withTarget(handle);
+	    }
+	}
 }

ProtocolLib/src/com/comphenix/protocol/events/PacketEvent.java

@@ -17,22 +17,30 @@
 
 package com.comphenix.protocol.events;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
 import java.util.EventObject;
 
 import org.bukkit.entity.Player;
 import org.bukkit.event.Cancellable;
 
+import com.comphenix.protocol.async.AsyncMarker;
+
 public class PacketEvent extends EventObject implements Cancellable {
 	/**
 	 * Automatically generated by Eclipse.
 	 */
 	private static final long serialVersionUID = -5360289379097430620L;
 
+	private transient Player player;
 	private PacketContainer packet;
-	private Player player;
 	private boolean serverPacket;
 	private boolean cancel;
 	
+	private AsyncMarker asyncMarker;
+	private boolean asynchronous;
+	
 	/**
 	 * Use the static constructors to create instances of this event.
 	 * @param source - the event source.
@@ -47,6 +55,16 @@ public class PacketEvent extends EventObject implements Cancellable {
 		this.player = player;
 		this.serverPacket = serverPacket;
 	}
+	
+	private PacketEvent(PacketEvent origial, AsyncMarker asyncMarker) {
+		super(origial.source);
+		this.packet = origial.packet;
+		this.player = origial.player;
+		this.cancel = origial.cancel;
+		this.serverPacket = origial.serverPacket;
+		this.asyncMarker = asyncMarker;
+		this.asynchronous = true;
+	}
 
 	/**
 	 * Creates an event representing a client packet transmission.
@@ -70,6 +88,16 @@ public class PacketEvent extends EventObject implements Cancellable {
 		return new PacketEvent(source, packet, recipient, true);
 	}
 	
+	/**
+	 * Create an asynchronous packet event from a synchronous event and a async marker.
+	 * @param event - the original synchronous event.
+	 * @param marker - the asynchronous marker.
+	 * @return The new packet event.
+	 */
+	public static PacketEvent fromSynchronous(PacketEvent event, AsyncMarker marker) {
+		return new PacketEvent(event, marker);
+	}
+	
 	/**
 	 * Retrieves the packet that will be sent to the player.
 	 * @return Packet to send to the player.
@@ -120,9 +148,67 @@ public class PacketEvent extends EventObject implements Cancellable {
 	
 	/**
 	 * Whether or not this packet was created by the server.
+	 * <p>
+	 * Most listeners can deduce this by noting which listener method was invoked.
 	 * @return TRUE if the packet was created by the server, FALSE if it was created by a client.
 	 */
 	public boolean isServerPacket() {
 		return serverPacket;
 	}
+	
+	/**
+	 * Retrieve the asynchronous marker.
+	 * <p>
+	 * If the packet is synchronous, this marker will be used to schedule an asynchronous event. In the following
+	 * asynchronous event, the marker is used to correctly pass the packet around to the different threads.
+	 * <p>
+	 * Note that if there are no asynchronous events that can receive this packet, the marker is NULL.
+	 * @return The current asynchronous marker, or NULL.
+	 */
+	public AsyncMarker getAsyncMarker() {
+		return asyncMarker;
+	}
+	/**
+	 * Set the asynchronous marker. 
+	 * <p>
+	 * If the marker is non-null at the end of an synchronous event processing, the packet will be scheduled
+	 * to be processed asynchronously with the given settings.
+	 * <p>
+	 * Note that if there are no asynchronous events that can receive this packet, the marker should be NULL. 
+	 * @param asyncMarker - the new asynchronous marker, or NULL.
+	 * @throws IllegalStateException If the current event is asynchronous.
+	 */
+	public void setAsyncMarker(AsyncMarker asyncMarker) {
+		if (isAsynchronous())
+			throw new IllegalStateException("The marker is immutable for asynchronous events");
+		this.asyncMarker = asyncMarker;
+	}
+
+	/**
+	 * Determine if the packet event has been executed asynchronously or not.
+	 * @return TRUE if this packet event is asynchronous, FALSE otherwise.
+	 */
+	public boolean isAsynchronous() {
+		return asynchronous;
+	}
+	
+	private void writeObject(ObjectOutputStream output) throws IOException {
+	    // Default serialization 
+		output.defaultWriteObject();
+
+		// Write the name of the player (or NULL if it's not set)
+		output.writeObject(player != null ? new SerializedOfflinePlayer(player) : null);
+	}
+
+	private void readObject(ObjectInputStream input) throws ClassNotFoundException, IOException {
+	    // Default deserialization
+		input.defaultReadObject();
+
+		final SerializedOfflinePlayer offlinePlayer = (SerializedOfflinePlayer) input.readObject();
+		
+	    if (offlinePlayer != null) {
+	    	// Better than nothing
+	    	player = offlinePlayer.getPlayer();
+	    }
+	}
 }

ProtocolLib/src/com/comphenix/protocol/events/SerializedOfflinePlayer.java

@@ -0,0 +1,216 @@
+package com.comphenix.protocol.events;
+
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.Serializable;
+import java.lang.reflect.Method;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import net.sf.cglib.proxy.Enhancer;
+import net.sf.cglib.proxy.MethodInterceptor;
+import net.sf.cglib.proxy.MethodProxy;
+
+import org.bukkit.Bukkit;
+import org.bukkit.Location;
+import org.bukkit.OfflinePlayer;
+import org.bukkit.World;
+import org.bukkit.entity.Player;
+
+/**
+ * Represents a player object that can be serialized by Java.
+ * 
+ * @author Kristian
+ */
+class SerializedOfflinePlayer implements OfflinePlayer, Serializable {
+
+	/**
+	 * Generated by Eclipse.
+	 */
+	private static final long serialVersionUID = -2728976288470282810L;
+
+	private transient Location bedSpawnLocation;
+	
+	// Relevant data about an offline player
+	private String name;
+	private long firstPlayed;
+	private long lastPlayed;
+	private boolean operator;
+	private boolean banned;
+	private boolean playedBefore;
+	private boolean online;
+	private boolean whitelisted;
+	
+	// Proxy helper
+	private static Map<String, Method> lookup = new ConcurrentHashMap<String, Method>();
+
+	/**
+	 * Constructor used by serialization.
+	 */
+	public SerializedOfflinePlayer() {
+		// Do nothing
+	}
+	
+	/**
+	 * Initialize this serializable offline player from another player.
+	 * @param offline - another player.
+	 */
+	public SerializedOfflinePlayer(OfflinePlayer offline) {
+		this.name = offline.getName();
+		this.firstPlayed = offline.getFirstPlayed();
+		this.lastPlayed = offline.getLastPlayed();
+		this.operator = offline.isOp();
+		this.banned = offline.isBanned();
+		this.playedBefore = offline.hasPlayedBefore();
+		this.online = offline.isOnline();
+		this.whitelisted = offline.isWhitelisted();
+	}
+	
+	@Override
+	public boolean isOp() {
+		return operator;
+	}
+
+	@Override
+	public void setOp(boolean operator) {
+		this.operator = operator;
+	}
+
+	@Override
+	public Map<String, Object> serialize() {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public Location getBedSpawnLocation() {
+		return bedSpawnLocation;
+	}
+
+	@Override
+	public long getFirstPlayed() {
+		return firstPlayed;
+	}
+
+	@Override
+	public long getLastPlayed() {
+		return lastPlayed;
+	}
+
+	@Override
+	public String getName() {
+		return name;
+	}
+	
+	@Override
+	public boolean hasPlayedBefore() {
+		return playedBefore;
+	}
+
+	@Override
+	public boolean isBanned() {
+		return banned;
+	}
+
+	@Override
+	public void setBanned(boolean banned) {
+		this.banned = banned;
+	}
+	
+	@Override
+	public boolean isOnline() {
+		return online;
+	}
+
+	@Override
+	public boolean isWhitelisted() {
+		return whitelisted;
+	}
+
+	@Override
+	public void setWhitelisted(boolean whitelisted) {
+		this.whitelisted = whitelisted;
+	}
+
+	private void writeObject(ObjectOutputStream output) throws IOException {
+		output.defaultWriteObject();
+		
+		// Serialize the bed spawn location
+		output.writeUTF(bedSpawnLocation.getWorld().getName());
+		output.writeDouble(bedSpawnLocation.getX());
+		output.writeDouble(bedSpawnLocation.getY());
+		output.writeDouble(bedSpawnLocation.getZ());
+	}
+	
+	private void readObject(ObjectInputStream input) throws ClassNotFoundException, IOException {
+		input.defaultReadObject();
+
+		// Well, this is a problem
+		bedSpawnLocation = new Location(
+				getWorld(input.readUTF()),
+				input.readDouble(),
+				input.readDouble(),
+				input.readDouble()
+		);
+	}
+	
+	private World getWorld(String name) {
+		try {
+			// Try to get the world at least
+			return Bukkit.getServer().getWorld(name);
+		} catch (Exception e) {
+			// Screw it
+			return null;
+		}
+	}
+	
+	@Override
+	public Player getPlayer() {
+		try {
+			// Try to get the real player underneath
+			return Bukkit.getServer().getPlayerExact(name);
+		} catch (Exception e) {
+			return getProxyPlayer();
+		}
+	}
+	
+	/**
+	 * Retrieve a player object that implements OfflinePlayer by refering to this object. 
+	 * <p>
+	 * All other methods cause an exception.
+	 * @return Proxy object.
+	 */
+	public Player getProxyPlayer() {
+		
+		// Remember to initialize the method filter
+		if (lookup.size() == 0) {
+			// Add all public methods
+			for (Method method : OfflinePlayer.class.getMethods()) {
+				lookup.put(method.getName(), method);
+			}
+		}
+		
+    	// MORE CGLIB magic!
+    	Enhancer ex = new Enhancer();
+    	ex.setSuperclass(Player.class);
+    	ex.setCallback(new MethodInterceptor() {
+			@Override
+			public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
+				
+				// There's no overloaded methods, so we don't care
+				Method offlineMethod = lookup.get(method.getName());
+				
+				// Ignore all other methods
+				if (offlineMethod == null) {
+					throw new UnsupportedOperationException(
+							"The method " + method.getName() + " is not supported for offline players.");
+				}
+
+				// Invoke our on method
+				return offlineMethod.invoke(SerializedOfflinePlayer.this, args);
+			}
+    	});
+    	
+    	return (Player) ex.create();
+	}
+}

ProtocolLib/src/com/comphenix/protocol/injector/ConcurrentListenerMultimap.java

@@ -1,194 +0,0 @@
-package com.comphenix.protocol.injector;
-
-import java.util.ArrayList;
-import java.util.List;
-import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentMap;
-import java.util.logging.Level;
-import java.util.logging.Logger;
-
-import com.comphenix.protocol.concurrency.SortedCopyOnWriteArray;
-import com.comphenix.protocol.events.ListenerPriority;
-import com.comphenix.protocol.events.ListeningWhitelist;
-import com.comphenix.protocol.events.PacketAdapter;
-import com.comphenix.protocol.events.PacketEvent;
-import com.comphenix.protocol.events.PacketListener;
-import com.google.common.base.Objects;
-import com.google.common.primitives.Ints;
-
-/**
- * A thread-safe implementation of a listener multimap.
- * 
- * @author Kristian
- */
-public class ConcurrentListenerMultimap {
-
-	// The core of our map
-	protected ConcurrentMap<Integer, SortedCopyOnWriteArray<PrioritizedListener>> listeners = 
-		  new ConcurrentHashMap<Integer, SortedCopyOnWriteArray<PrioritizedListener>>();
-	
-	/**
-	 * Adds a listener to its requested list of packet recievers.
-	 * @param listener - listener with a list of packets to recieve notifcations for.
-	 * @param whitelist - the packet whitelist to use.
-	 */
-	public void addListener(PacketListener listener, ListeningWhitelist whitelist) {
-		
-		PrioritizedListener prioritized = new PrioritizedListener(listener, whitelist.getPriority());
-		
-		for (Integer packetID : whitelist.getWhitelist()) {
-			addListener(packetID, prioritized);
-		}
-	}
-	
-	// Add the listener to a specific packet notifcation list
-	private void addListener(Integer packetID, PrioritizedListener listener) {
-		
-		SortedCopyOnWriteArray<PrioritizedListener> list = listeners.get(packetID);
-		
-		// We don't want to create this for every lookup
-		if (list == null) {
-			// It would be nice if we could use a PriorityBlockingQueue, but it doesn't preseve iterator order,
-			// which is a essential feature for our purposes.
-			final SortedCopyOnWriteArray<PrioritizedListener> value = new SortedCopyOnWriteArray<PrioritizedListener>();
-			
-			list = listeners.putIfAbsent(packetID, value);
-			
-			// We may end up creating multiple multisets, but we'll agree 
-			// on the one to use.
-			if (list == null) {
-				list = value;
-			}
-		}
-		
-		// Thread safe
-		list.add(listener);
-	}
-	
-	/**
-	 * Removes the given listener from the packet event list.
-	 * @param listener - listener to remove.
-	 * @param whitelist - the packet whitelist that was used.
-	 * @return Every packet ID that was removed due to no listeners.
-	 */
-	public List<Integer> removeListener(PacketListener listener, ListeningWhitelist whitelist) {
-	
-		List<Integer> removedPackets = new ArrayList<Integer>();
-		
-		// Again, not terribly efficient. But adding or removing listeners should be a rare event.
-		for (Integer packetID : whitelist.getWhitelist()) {
-			
-			SortedCopyOnWriteArray<PrioritizedListener> list = listeners.get(packetID);
-			
-			// Remove any listeners
-			if (list != null) {
-				// Don't remove from newly created lists
-				if (list.size() > 0) {
-					// Remove this listener. Note that priority is generally ignored.
-					list.remove(new PrioritizedListener(listener, whitelist.getPriority()));
-					
-					if (list.size() == 0) {
-						listeners.remove(packetID);
-						removedPackets.add(packetID);
-					}
-				}
-			}
-			
-			// Move on to the next
-		}
-		
-		return removedPackets;
-	}
-	
-	/**
-	 * Invokes the given packet event for every registered listener.
-	 * @param logger - the logger that will be used to inform about listener exceptions.
-	 * @param event - the packet event to invoke.
-	 */
-	public void invokePacketRecieving(Logger logger, PacketEvent event) {
-		SortedCopyOnWriteArray<PrioritizedListener> list = listeners.get(event.getPacketID());
-		
-		if (list == null)
-			return;
-		
-		// We have to be careful. Cannot modify the underlying list when sending notifications.
-		synchronized (list) {
-			for (PrioritizedListener element : list) {
-				try {
-					element.getListener().onPacketReceiving(event);
-				} catch (Throwable e) {
-					// Minecraft doesn't want your Exception.
-					logger.log(Level.SEVERE, 
-							"Exception occured in onPacketReceiving() for " + 
-								PacketAdapter.getPluginName(element.getListener()), e);
-				}
-			}
-		}
-	}
-	
-	/**
-	 * Invokes the given packet event for every registered listener.
-	 * @param logger - the logger that will be used to inform about listener exceptions.
-	 * @param event - the packet event to invoke.
-	 */
-	public void invokePacketSending(Logger logger, PacketEvent event) {
-		SortedCopyOnWriteArray<PrioritizedListener> list = listeners.get(event.getPacketID());
-		
-		if (list == null)
-			return;
-		
-		synchronized (list) {
-			for (PrioritizedListener element : list) {
-				try {
-					element.getListener().onPacketSending(event);
-				} catch (Throwable e) {
-					// Minecraft doesn't want your Exception.
-					logger.log(Level.SEVERE, 
-							"Exception occured in onPacketReceiving() for " + 
-								PacketAdapter.getPluginName(element.getListener()), e);
-				}
-			}
-		}	
-	}
-	
-	/**
-	 * A listener with an associated priority.
-	 */
-	private class PrioritizedListener implements Comparable<PrioritizedListener> {
-		private PacketListener listener;
-		private ListenerPriority priority;
-		
-		public PrioritizedListener(PacketListener listener, ListenerPriority priority) {
-			this.listener = listener;
-			this.priority = priority;
-		}
-
-		@Override
-		public int compareTo(PrioritizedListener other) {
-			// This ensures that lower priority listeners are executed first
-			return Ints.compare(this.getPriority().getSlot(),
-					            other.getPriority().getSlot());
-		}
-		
-		// Note that this equals() method is NOT consistent with compareTo(). 
-		// But, it's a private class so who cares.
-		@Override
-		public boolean equals(Object obj) {
-			// We only care about the listener - priority itself should not make a difference
-		    if(obj instanceof PrioritizedListener){
-		        final PrioritizedListener other = (PrioritizedListener) obj;
-		        return Objects.equal(listener, other.listener);
-		    } else {
-		        return false;
-		    }
-		}
-		
-		public PacketListener getListener() {
-			return listener;
-		}
-
-		public ListenerPriority getPriority() {
-			return priority;
-		}
-	}
-}

ProtocolLib/src/com/comphenix/protocol/injector/EntityUtilities.java

@@ -35,8 +35,39 @@ class EntityUtilities {
 	private static Method hashGetMethod;
 	private static Method scanPlayersMethod;
 	
+	/*
+	 * While this function may look pretty bad, it's essentially just a reflection-warped 
+	 * version of the following:
+	 * 
+	 *  	@SuppressWarnings("unchecked")
+	 *	 	public static void updateEntity2(Entity entity, List<Player> observers) {
+	 *
+	 *			World world = entity.getWorld();
+	 *			WorldServer worldServer = ((CraftWorld) world).getHandle();
+	 *
+	 *			EntityTracker tracker = worldServer.tracker;
+	 *			EntityTrackerEntry entry = (EntityTrackerEntry) tracker.trackedEntities.get(entity.getEntityId());
+	 *
+	 *			List<EntityPlayer> nmsPlayers = getNmsPlayers(observers);
+	 *
+	 *			entry.trackedPlayers.removeAll(nmsPlayers);
+	 *			entry.scanPlayers(nmsPlayers);
+	 *		}
+	 *
+	 *		private static List<EntityPlayer> getNmsPlayers(List<Player> players) {
+	 *			List<EntityPlayer> nsmPlayers = new ArrayList<EntityPlayer>();
+	 *	
+	 *			for (Player bukkitPlayer : players) {
+	 *				CraftPlayer craftPlayer = (CraftPlayer) bukkitPlayer;
+	 *				nsmPlayers.add(craftPlayer.getHandle());
+	 *			}
+	 *	
+	 *			return nsmPlayers;
+	 *		}
+	 *
+	 */
 	public static void updateEntity(Entity entity, List<Player> observers) throws FieldAccessException {
-
+		
 		World world = entity.getWorld();
 		Object worldServer = ((CraftWorld) world).getHandle();
 

ProtocolLib/src/com/comphenix/protocol/injector/InjectedServerConnection.java

@@ -0,0 +1,189 @@
+package com.comphenix.protocol.injector;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import org.bukkit.Server;
+
+import com.comphenix.protocol.reflect.FieldUtils;
+import com.comphenix.protocol.reflect.FuzzyReflection;
+import com.comphenix.protocol.reflect.VolatileField;
+
+/**
+ * Used to ensure that the 1.3 server is referencing the correct server handler.
+ * 
+ * @author Kristian
+ */
+class InjectedServerConnection {
+	
+	private static Field listenerThreadField;
+	private static Field minecraftServerField;
+	private static Method serverConnectionMethod;
+	private static Field listField;
+	
+	private List<VolatileField> listFields;
+	private List<ReplacedArrayList<Object>> replacedLists;
+	
+	private Server server;
+	private Logger logger;
+	private boolean hasAttempted;
+	private boolean hasSuccess;
+	
+	private Object minecraftServer = null;
+	
+	public InjectedServerConnection(Logger logger, Server server) {
+		this.listFields = new ArrayList<VolatileField>();
+		this.replacedLists = new ArrayList<ReplacedArrayList<Object>>();
+		this.logger = logger;
+		this.server = server;
+	}
+
+	public void injectList() {
+
+		// Only execute this method once
+		if (!hasAttempted)
+			hasAttempted = true;
+		else
+			return;
+		
+		if (minecraftServerField == null)
+			minecraftServerField = FuzzyReflection.fromObject(server, true).getFieldByType(".*MinecraftServer");
+
+		try {
+			minecraftServer = FieldUtils.readField(minecraftServerField, server, true);
+		} catch (IllegalAccessException e1) {
+			logger.log(Level.WARNING, "Cannot extract minecraft server from Bukkit.");
+			return;
+		}
+		
+		try {
+			if (serverConnectionMethod == null)
+				serverConnectionMethod = FuzzyReflection.fromClass(minecraftServerField.getType()).
+											getMethodByParameters("getServerConnection", ".*ServerConnection", new String[] {});
+			// We're using Minecraft 1.3.1
+			injectServerConnection();
+		
+		} catch (RuntimeException e) {
+			
+			// Minecraft 1.2.5 or lower
+			injectListenerThread();
+		}
+	}
+	
+	private void injectListenerThread() {
+	
+		try {
+		
+		if (listenerThreadField == null)
+			listenerThreadField = FuzzyReflection.fromClass(minecraftServerField.getType()).
+				getFieldByType(".*NetworkListenThread");
+		} catch (RuntimeException e) {
+			logger.log(Level.SEVERE, "Cannot find listener thread in MinecraftServer.");
+			return;
+		}
+
+		Object listenerThread = null;
+		
+		// Attempt to get the thread
+		try {
+			listenerThread = listenerThreadField.get(minecraftServer);
+		} catch (Exception e) {
+			logger.log(Level.WARNING, "Unable to read the listener thread.");
+			return;
+		}
+		
+		// Ok, great. Get every list field
+		List<Field> lists = FuzzyReflection.fromClass(listenerThreadField.getType()).getFieldListByType(List.class);
+		
+		for (Field list : lists) {
+			injectIntoList(listenerThread, list);
+		}
+		
+		hasSuccess = true;
+	}
+	
+	private void injectServerConnection() {
+		
+		Object serverConnection = null;
+		
+		// Careful - we might fail
+		try {
+			serverConnection = serverConnectionMethod.invoke(minecraftServer);
+		} catch (Exception ex) {
+			logger.log(Level.WARNING, "Unable to retrieve server connection", ex);
+			return;
+		}
+		
+		if (listField == null)
+			listField = FuzzyReflection.fromClass(serverConnectionMethod.getReturnType(), true).
+							getFieldByType("serverConnection", List.class);
+		injectIntoList(serverConnection, listField);
+		hasSuccess = true;
+	}
+	
+	@SuppressWarnings("unchecked")
+	private void injectIntoList(Object instance, Field field) {
+		VolatileField listFieldRef = new VolatileField(listField, instance, true);
+		List<Object> list = (List<Object>) listFieldRef.getValue();
+
+		// Careful not to inject twice
+		if (list instanceof ReplacedArrayList) {
+			replacedLists.add((ReplacedArrayList<Object>) list);
+		} else {
+			replacedLists.add(new ReplacedArrayList<Object>(list));
+			listFieldRef.setValue(replacedLists.get(0));
+			listFields.add(listFieldRef);
+		}
+	}
+	
+	/**
+	 * Replace the server handler instance kept by the "keep alive" object.
+	 * @param oldHandler - old server handler.
+	 * @param newHandler - new, proxied server handler.
+	 */
+	public void replaceServerHandler(Object oldHandler, Object newHandler) {
+		if (!hasAttempted) {
+			injectList();
+		}
+		
+		if (hasSuccess) {
+			for (ReplacedArrayList<Object> replacedList : replacedLists) {
+				replacedList.addMapping(oldHandler, newHandler);
+			}
+		}
+	}
+	
+	/**
+	 * Revert to the old vanilla server handler, if it has been replaced.
+	 * @param oldHandler - old vanilla server handler.
+	 */
+	public void revertServerHandler(Object oldHandler) {
+		if (hasSuccess) {
+			for (ReplacedArrayList<Object> replacedList : replacedLists) {
+				replacedList.removeMapping(oldHandler);
+			}
+		}
+	}
+	
+	/**
+	 * Undoes everything.
+	 */
+	public void cleanupAll() {
+		if (replacedLists.size() > 0) {
+			// Repair the underlying lists
+			for (ReplacedArrayList<Object> replacedList : replacedLists) {
+				replacedList.revertAll();
+			}
+			for (VolatileField field : listFields) {
+				field.revertValue();
+			}
+			
+			listFields.clear();
+			replacedLists.clear();
+		}
+	}
+}

ProtocolLib/src/com/comphenix/protocol/injector/MinecraftRegistry.java

@@ -49,7 +49,7 @@ class MinecraftRegistry {
 		// Initialize it, if we haven't already
 		if (packetToID == null) {
 			try {
-				Field packetsField = FuzzyReflection.fromClass(Packet.class, true).getFieldByType("java\\.util\\.Map");
+				Field packetsField = FuzzyReflection.fromClass(Packet.class, true).getFieldByType("packetsField", Map.class);
 				packetToID = (Map<Class, Integer>) FieldUtils.readStaticField(packetsField, true);
 				
 			} catch (IllegalAccessException e) {
@@ -88,8 +88,8 @@ class MinecraftRegistry {
 		Map<Integer, Class> lookup = forceVanilla ? previousValues : overwrittenPackets;
 		
 		// Optimized lookup
-		if (lookup.containsKey(packetToID)) {
-			return lookup.get(packetToID);
+		if (lookup.containsKey(packetID)) {
+			return lookup.get(packetID);
 		}
 
 		// Will most likely not be used

ProtocolLib/src/com/comphenix/protocol/injector/NetworkFieldInjector.java

@@ -10,6 +10,9 @@ import java.util.concurrent.ConcurrentHashMap;
 
 import org.bukkit.entity.Player;
 
+import com.comphenix.protocol.Packets;
+import com.comphenix.protocol.events.ListeningWhitelist;
+import com.comphenix.protocol.events.PacketListener;
 import com.comphenix.protocol.reflect.FieldUtils;
 import com.comphenix.protocol.reflect.FuzzyReflection;
 import com.comphenix.protocol.reflect.StructureModifier;
@@ -48,7 +51,7 @@ class NetworkFieldInjector extends PlayerInjector {
 	}
 	
 	@Override
-	protected void initialize() throws IllegalAccessException {
+	protected synchronized void initialize() throws IllegalAccessException {
 		super.initialize();
 	
 		// Get the sync field as well
@@ -83,6 +86,15 @@ class NetworkFieldInjector extends PlayerInjector {
 		}
 	}
 	
+	@Override
+	public void checkListener(PacketListener listener) {
+		// Unfortunately, we don't support chunk packets
+		if (ListeningWhitelist.containsAny(listener.getSendingWhitelist(), 
+				Packets.Server.MAP_CHUNK, Packets.Server.MAP_CHUNK_BULK)) {
+			throw new IllegalStateException("The NETWORK_FIELD_INJECTOR hook doesn't support map chunk listeners.");
+		}
+	}
+	
 	@Override
 	public void injectManager() {
 		

ProtocolLib/src/com/comphenix/protocol/injector/NetworkObjectInjector.java

@@ -11,6 +11,10 @@ import java.util.Set;
 
 import org.bukkit.entity.Player;
 
+import com.comphenix.protocol.Packets;
+import com.comphenix.protocol.events.ListeningWhitelist;
+import com.comphenix.protocol.events.PacketListener;
+
 /**
  * Injection method that overrides the NetworkHandler itself, and it's sendPacket-method.
  * 
@@ -42,6 +46,15 @@ class NetworkObjectInjector extends PlayerInjector {
 		}
 	}
 	
+	@Override
+	public void checkListener(PacketListener listener) {
+		// Unfortunately, we don't support chunk packets
+		if (ListeningWhitelist.containsAny(listener.getSendingWhitelist(), 
+				Packets.Server.MAP_CHUNK, Packets.Server.MAP_CHUNK_BULK)) {
+			throw new IllegalStateException("The NETWORK_FIELD_INJECTOR hook doesn't support map chunk listeners.");
+		}
+	}
+	
 	@Override
 	public void injectManager() {
 		

ProtocolLib/src/com/comphenix/protocol/injector/NetworkServerInjector.java

@@ -0,0 +1,181 @@
+package com.comphenix.protocol.injector;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Set;
+
+import net.minecraft.server.Packet;
+import net.sf.cglib.proxy.Enhancer;
+import net.sf.cglib.proxy.Factory;
+import net.sf.cglib.proxy.MethodInterceptor;
+import net.sf.cglib.proxy.MethodProxy;
+
+import org.bukkit.entity.Player;
+
+import com.comphenix.protocol.events.PacketListener;
+import com.comphenix.protocol.reflect.FieldAccessException;
+import com.comphenix.protocol.reflect.FieldUtils;
+import com.comphenix.protocol.reflect.FuzzyReflection;
+import com.comphenix.protocol.reflect.StructureModifier;
+import com.comphenix.protocol.reflect.instances.CollectionGenerator;
+import com.comphenix.protocol.reflect.instances.DefaultInstances;
+import com.comphenix.protocol.reflect.instances.ExistingGenerator;
+import com.comphenix.protocol.reflect.instances.PrimitiveGenerator;
+
+/**
+ * Represents a player hook into the NetServerHandler class. 
+ * 
+ * @author Kristian
+ */
+public class NetworkServerInjector extends PlayerInjector {
+
+	private static Method sendPacketMethod;
+
+	private StructureModifier<Object> serverHandlerModifier;
+	private InjectedServerConnection serverInjection;
+	
+	public NetworkServerInjector(Player player, PacketFilterManager manager, 
+								 Set<Integer> sendingFilters, InjectedServerConnection serverInjection) throws IllegalAccessException {
+		super(player, manager, sendingFilters);
+		this.serverInjection = serverInjection;
+	}
+	
+	@Override
+	protected void initialize() throws IllegalAccessException {
+		super.initialize();
+		
+		// Get the send packet method!
+		if (hasInitialized) {
+			if (sendPacketMethod == null)
+				sendPacketMethod = FuzzyReflection.fromObject(serverHandler).getMethodByName("sendPacket.*");
+			if (serverHandlerModifier == null)
+				serverHandlerModifier = new StructureModifier<Object>(serverHandler.getClass(), null, false);
+		}
+	}
+
+	@Override
+	public void sendServerPacket(Packet packet, boolean filtered) throws InvocationTargetException {
+		Object serverDeleage = filtered ? serverHandlerRef.getValue() : serverHandlerRef.getOldValue();
+		
+		if (serverDeleage != null) {
+			try {
+				// Note that invocation target exception is a wrapper for a checked exception
+				sendPacketMethod.invoke(serverDeleage, packet);
+				
+			} catch (IllegalArgumentException e) {
+				throw e;
+			} catch (InvocationTargetException e) {
+				throw e;
+			} catch (IllegalAccessException e) {
+				throw new IllegalStateException("Unable to access send packet method.", e);
+			}
+		} else {
+			throw new IllegalStateException("Unable to load server handler. Cannot send packet.");
+		}
+	}
+
+	@Override
+	public void injectManager() {
+		
+		if (serverHandlerRef == null)
+			throw new IllegalStateException("Cannot find server handler.");
+		// Don't inject twice
+		if (serverHandlerRef.getValue() instanceof Factory)
+			return;
+		
+		Class<?> serverClass = serverHandler.getClass();
+		
+		Enhancer ex = new Enhancer();
+		ex.setClassLoader(manager.getClassLoader());
+		ex.setSuperclass(serverClass);
+		ex.setCallback(new MethodInterceptor() {
+			@Override
+			public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
+				
+				// The send packet method!
+				if (method.equals(sendPacketMethod)) {
+					Packet packet = (Packet) args[0];
+					
+					if (packet != null) {
+						packet = handlePacketRecieved(packet);
+						
+						// A NULL packet indicate cancelling
+						if (packet != null)
+							args[0] = packet;
+						else
+							return null;
+					}
+				}
+				
+				// Call the method directly
+				return proxy.invokeSuper(obj, args);
+			}
+		});
+		
+		// Use the existing field values when we create our copy
+		DefaultInstances serverInstances = DefaultInstances.fromArray(
+				ExistingGenerator.fromObjectFields(serverHandler),
+				PrimitiveGenerator.INSTANCE, 
+				CollectionGenerator.INSTANCE);
+
+		Object proxyObject = serverInstances.forEnhancer(ex).getDefault(serverClass);
+		serverInjection.replaceServerHandler(serverHandler, proxyObject);
+		
+		// Inject it now
+		if (proxyObject != null) {
+			copyTo(serverHandler, proxyObject);
+			serverHandlerRef.setValue(proxyObject);
+		} else {
+			throw new RuntimeException(
+					"Cannot hook player: Unable to find a valid constructor for the NetServerHandler object.");
+		}
+	}
+	
+	/**
+	 * Copy every field in server handler A to server handler B.
+	 * @param source - fields to copy.
+	 * @param destination - fields to copy to.
+	 */
+	private void copyTo(Object source, Object destination) {
+		StructureModifier<Object> modifierSource = serverHandlerModifier.withTarget(source);
+		StructureModifier<Object> modifierDest = serverHandlerModifier.withTarget(destination);
+		
+		// Copy every field
+		try {
+			for (int i = 0; i < modifierSource.size(); i++) {
+					modifierDest.write(i, modifierSource.read(i));
+			}
+		} catch (FieldAccessException e) {
+			throw new RuntimeException("Unable to copy fields from NetServerHandler.", e);
+		}
+	}
+	
+	@Override
+	public void cleanupAll() {
+		if (serverHandlerRef != null && serverHandlerRef.isCurrentSet()) {
+			copyTo(serverHandlerRef.getValue(), serverHandlerRef.getOldValue());
+			serverHandlerRef.revertValue();
+		}
+		
+		serverInjection.revertServerHandler(serverHandler);
+		
+		try {
+			if (getNetHandler() != null) {
+				// Restore packet listener
+				try {
+					FieldUtils.writeField(netHandlerField, networkManager, serverHandlerRef.getOldValue(), true);
+				} catch (IllegalAccessException e) {
+					// Oh well
+					e.printStackTrace();
+				}
+			}
+		} catch (IllegalAccessException e) {
+			e.printStackTrace();
+		}
+	}
+	
+	@Override
+	public void checkListener(PacketListener listener) {
+		// We support everything
+	}
+}

ProtocolLib/src/com/comphenix/protocol/injector/PacketFilterManager.java

@@ -34,6 +34,7 @@ import net.sf.cglib.proxy.Enhancer;
 import net.sf.cglib.proxy.MethodInterceptor;
 import net.sf.cglib.proxy.MethodProxy;
 
+import org.bukkit.Server;
 import org.bukkit.entity.Entity;
 import org.bukkit.entity.Player;
 import org.bukkit.event.EventHandler;
@@ -45,7 +46,10 @@ import org.bukkit.event.server.PluginDisableEvent;
 import org.bukkit.plugin.Plugin;
 import org.bukkit.plugin.PluginManager;
 
+import com.comphenix.protocol.AsynchronousManager;
 import com.comphenix.protocol.ProtocolManager;
+import com.comphenix.protocol.async.AsyncFilterManager;
+import com.comphenix.protocol.async.AsyncMarker;
 import com.comphenix.protocol.events.*;
 import com.comphenix.protocol.reflect.FieldAccessException;
 import com.comphenix.protocol.reflect.FuzzyReflection;
@@ -60,14 +64,23 @@ public final class PacketFilterManager implements ProtocolManager {
 	 */
 	public enum PlayerInjectHooks {
 		/**
-		 * Override the packet queue lists in NetworkHandler.
+		 * Override the packet queue lists in NetworkHandler. 
+		 * <p>
+		 * Cannot intercept MapChunk packets. 
 		 */
 		NETWORK_HANDLER_FIELDS,
 		
 		/**
-		 * Override the network handler object itself.
+		 * Override the network handler object itself. Only works in 1.3.
+		 * <p>
+		 * Cannot intercept MapChunk packets. 
 		 */
-		NETWORK_MANAGER_OBJECT
+		NETWORK_MANAGER_OBJECT,
+		
+		/**
+		 * Override the server handler object. Versatile, but a tad slower.
+		 */
+		NETWORK_SERVER_OBJECT;
 	}
 	
 	// Create a concurrent set
@@ -84,26 +97,35 @@ public final class PacketFilterManager implements ProtocolManager {
 	// Packet injection
 	private PacketInjector packetInjector;
 	
+	// Server connection injection
+	private InjectedServerConnection serverInjection;
+	
 	// Enabled packet filters
 	private Set<Integer> sendingFilters = Collections.newSetFromMap(new ConcurrentHashMap<Integer, Boolean>());
 	
 	// The two listener containers
-	private ConcurrentListenerMultimap recievedListeners = new ConcurrentListenerMultimap();
-	private ConcurrentListenerMultimap sendingListeners = new ConcurrentListenerMultimap();
+	private SortedPacketListenerList recievedListeners = new SortedPacketListenerList();
+	private SortedPacketListenerList sendingListeners = new SortedPacketListenerList();
 	
 	// Whether or not this class has been closed
-	private boolean hasClosed;
+	private volatile boolean hasClosed;
 	
 	// The default class loader
 	private ClassLoader classLoader;
 	
+	// The last successful player hook
+	private PlayerInjector lastSuccessfulHook;
+	
 	// Error logger
 	private Logger logger;
 	
+	// The async packet handler
+	private AsyncFilterManager asyncFilterManager;
+	
 	/**
 	 * Only create instances of this class if protocol lib is disabled.
 	 */
-	public PacketFilterManager(ClassLoader classLoader, Logger logger) {
+	public PacketFilterManager(ClassLoader classLoader, Server server, Logger logger) {
 		if (logger == null)
 			throw new IllegalArgumentException("logger cannot be NULL.");
 		if (classLoader == null)
@@ -114,11 +136,18 @@ public final class PacketFilterManager implements ProtocolManager {
 			this.classLoader = classLoader;
 			this.logger = logger;
 			this.packetInjector = new PacketInjector(classLoader, this, connectionLookup);
+			this.asyncFilterManager = new AsyncFilterManager(logger, server.getScheduler(), this);
+			this.serverInjection = new InjectedServerConnection(logger, server);
 		} catch (IllegalAccessException e) {
 			logger.log(Level.SEVERE, "Unable to initialize packet injector.", e);
 		}
 	}
 	
+	@Override
+	public AsynchronousManager getAsynchronousManager() {
+		return asyncFilterManager;
+	}
+	
 	/**
 	 * Retrieves how the server packets are read.
 	 * @return Injection method for reading server packets.
@@ -133,6 +162,13 @@ public final class PacketFilterManager implements ProtocolManager {
 	 */
 	public void setPlayerHook(PlayerInjectHooks playerHook) {
 		this.playerHook = playerHook;
+		
+		// Make sure the current listeners are compatible
+		if (lastSuccessfulHook != null) {
+			for (PacketListener listener : packetListeners) {
+				checkListener(listener);
+			}
+		}
 	}
 
 	public Logger getLogger() {
@@ -161,12 +197,17 @@ public final class PacketFilterManager implements ProtocolManager {
 		if (hasSending || hasReceiving) {
 			// Add listeners and hooks
 			if (hasSending) {
+				verifyWhitelist(listener, sending);
 				sendingListeners.addListener(listener, sending);
 				enablePacketFilters(ConnectionSide.SERVER_SIDE, sending.getWhitelist());
 			}
 			if (hasReceiving) {
+				verifyWhitelist(listener, receiving);
 				recievedListeners.addListener(listener, receiving);
 				enablePacketFilters(ConnectionSide.CLIENT_SIDE, receiving.getWhitelist());
+				
+				// We don't know if we've hooked any players yet
+				checkListener(listener);
 			}
 			
 			// Inform our injected hooks
@@ -174,6 +215,36 @@ public final class PacketFilterManager implements ProtocolManager {
 		}
 	}
 	
+	/**
+	 * Determine if the packet IDs in a whitelist is valid.
+	 * @param listener - the listener that will be mentioned in the error.
+	 * @param whitelist - whitelist of packet IDs.
+	 * @throws IllegalArgumentException If the whitelist is illegal.
+	 */
+	public static void verifyWhitelist(PacketListener listener, ListeningWhitelist whitelist) {
+		for (Integer id : whitelist.getWhitelist()) {
+			if (id >= 256 || id < 0) {
+				throw new IllegalArgumentException(String.format("Invalid packet id %s in listener %s.", 
+							id, PacketAdapter.getPluginName(listener))
+				);
+			}
+		}
+	}
+	
+	/**
+	 * Determine if a listener is valid or not.
+	 * @param listener - listener to check.
+	 * @throws IllegalStateException If the given listener's whitelist cannot be fulfilled.
+	 */
+	public void checkListener(PacketListener listener) {
+		try {
+			if (lastSuccessfulHook != null)
+				lastSuccessfulHook.checkListener(listener);
+		} catch (Exception e) {
+			throw new IllegalStateException("Registering listener " + PacketAdapter.getPluginName(listener) + " failed", e);
+		}
+	}
+	
 	@Override
 	public void removePacketListener(PacketListener listener) {
 		if (listener == null)
@@ -212,6 +283,9 @@ public final class PacketFilterManager implements ProtocolManager {
 				removePacketListener(listener);
 			}
 		}
+		
+		// Do the same for the asynchronous events
+		asyncFilterManager.unregisterAsyncHandlers(plugin);
 	}
 	
 	/**
@@ -219,7 +293,7 @@ public final class PacketFilterManager implements ProtocolManager {
 	 * @param event - the packet event to invoke.
 	 */
 	public void invokePacketRecieving(PacketEvent event) {
-		recievedListeners.invokePacketRecieving(logger, event);
+		handlePacket(recievedListeners, event, false);
 	}
 	
 	/**
@@ -227,7 +301,41 @@ public final class PacketFilterManager implements ProtocolManager {
 	 * @param event - the packet event to invoke.
 	 */
 	public void invokePacketSending(PacketEvent event) {
-		sendingListeners.invokePacketSending(logger, event);
+		handlePacket(sendingListeners, event, true);
+	}
+	
+	/**
+	 * Handle a packet sending or receiving event.
+	 * <p>
+	 * Note that we also handle asynchronous events.
+	 * @param packetListeners - packet listeners that will receive this event.
+	 * @param event - the evnet to broadcast.
+	 */
+	private void handlePacket(SortedPacketListenerList packetListeners, PacketEvent event, boolean sending) {
+		
+		// By default, asynchronous packets are queued for processing
+		if (asyncFilterManager.hasAsynchronousListeners(event)) {
+			event.setAsyncMarker(asyncFilterManager.createAsyncMarker());
+		}
+		
+		// Process synchronous events
+		if (sending)
+			packetListeners.invokePacketSending(logger, event);
+		else
+			packetListeners.invokePacketRecieving(logger, event);
+		
+		// To cancel asynchronous processing, use the async marker
+		if (!event.isCancelled() && !hasAsyncCancelled(event.getAsyncMarker())) {
+			asyncFilterManager.enqueueSyncPacket(event, event.getAsyncMarker());
+
+			// The above makes a copy of the event, so it's safe to cancel it
+			event.setCancelled(true);
+		}
+	}
+	
+	// NULL marker mean we're dealing with no asynchronous listeners 
+	private boolean hasAsyncCancelled(AsyncMarker marker) {
+		return marker == null || marker.isAsyncCancelled();
 	}
 	
 	/**
@@ -298,6 +406,9 @@ public final class PacketFilterManager implements ProtocolManager {
 		PlayerInjector injector = getInjector(sender);
 		Packet mcPacket = packet.getHandle();
 		
+		// Make sure the packet isn't cancelled
+		packetInjector.undoCancel(packet.getID(), mcPacket);
+		
 		if (filters) {
 			mcPacket = injector.handlePacketRecieved(mcPacket);
 		}
@@ -343,8 +454,6 @@ public final class PacketFilterManager implements ProtocolManager {
 	
 	@Override
 	public void updateEntity(Entity entity, List<Player> observers) throws FieldAccessException {
-		
-		
 		EntityUtilities.updateEntity(entity, observers);
 	}
 	
@@ -360,20 +469,22 @@ public final class PacketFilterManager implements ProtocolManager {
 	/**
 	 * Used to construct a player hook.
 	 * @param player - the player to hook.
+	 * @param hook - the hook type.
 	 * @return A new player hoook
 	 * @throws IllegalAccessException Unable to do our reflection magic.
 	 */
-	protected PlayerInjector getPlayerHookInstance(Player player) throws IllegalAccessException {
-		
+	protected PlayerInjector getHookInstance(Player player, PlayerInjectHooks hook) throws IllegalAccessException {
 		// Construct the correct player hook
-		switch (playerHook) {
+		switch (hook) {
 		case NETWORK_HANDLER_FIELDS: 
 			return new NetworkFieldInjector(player, this, sendingFilters);
 		case NETWORK_MANAGER_OBJECT: 
 			return new NetworkObjectInjector(player, this, sendingFilters);
+		case NETWORK_SERVER_OBJECT:
+			return new NetworkServerInjector(player, this, sendingFilters, serverInjection);
+		default:
+			throw new IllegalArgumentException("Cannot construct a player injector.");
 		}
-		
-		throw new IllegalArgumentException("Cannot construct a player injector.");
 	}
 	
 	/**
@@ -381,20 +492,51 @@ public final class PacketFilterManager implements ProtocolManager {
 	 * @param player - player to hook.
 	 */
 	protected void injectPlayer(Player player) {
+		
+		PlayerInjector injector = null;
+		PlayerInjectHooks currentHook = playerHook;
+		boolean firstPlayer = lastSuccessfulHook == null;
+		
 		// Don't inject if the class has closed
 		if (!hasClosed && player != null && !playerInjection.containsKey(player)) {
-			try {
-				PlayerInjector injector = getPlayerHookInstance(player);
+			while (true) {
+				try {
+					injector = getHookInstance(player, currentHook);
+					injector.injectManager();
+					playerInjection.put(player, injector);
+					connectionLookup.put(injector.getInputStream(false), player);
+					break;
+					
+				} catch (Exception e) {
 
-				injector.injectManager();
-				playerInjection.put(player, injector);
-				connectionLookup.put(injector.getInputStream(false), player);
-				
-			} catch (IllegalAccessException e) {
-				// Mark this injection attempt as a failure
-				playerInjection.put(player, null);
-				logger.log(Level.SEVERE, "Unable to access fields.", e);
+					// Mark this injection attempt as a failure
+					logger.log(Level.SEVERE, "Player hook " + currentHook.toString() + " failed.", e);
+					
+					// Clean up as much as possible
+					try {
+						if (injector != null)
+							injector.cleanupAll();
+					} catch (Exception e2) {
+						logger.log(Level.WARNING, "Cleaing up after player hook failed.", e);
+					}
+					
+					if (currentHook.ordinal() > 0) {
+						// Choose the previous player hook type
+						currentHook = PlayerInjectHooks.values()[currentHook.ordinal() - 1];
+						logger.log(Level.INFO, "Switching to " + currentHook.toString() + " instead.");
+					} else {
+						// UTTER FAILURE
+						playerInjection.put(player, null);
+						return;
+					}
+				}
 			}
+			
+			// Update values
+			if (injector != null)
+				lastSuccessfulHook = injector;
+			if (currentHook != playerHook || firstPlayer) 
+				setPlayerHook(currentHook);
 		}
 	}
 	
@@ -477,7 +619,7 @@ public final class PacketFilterManager implements ProtocolManager {
 						if (event instanceof PlayerJoinEvent)
 							injectPlayer(((PlayerJoinEvent) event).getPlayer());
 						else if (event instanceof PlayerQuitEvent)
-							injectPlayer(((PlayerQuitEvent) event).getPlayer());
+							uninjectPlayer(((PlayerQuitEvent) event).getPlayer());
 					}
 					return null;
 				}
@@ -524,12 +666,12 @@ public final class PacketFilterManager implements ProtocolManager {
 		if (!hasClosed && player != null) {
 			
 			PlayerInjector injector = playerInjection.get(player);
-			DataInputStream input = injector.getInputStream(true);
 			
 			if (injector != null) {
+				DataInputStream input = injector.getInputStream(true);
 				injector.cleanupAll();
 				
-				playerInjection.remove(injector);
+				playerInjection.remove(player);
 				connectionLookup.remove(input);
 			}
 		}	
@@ -565,23 +707,31 @@ public final class PacketFilterManager implements ProtocolManager {
 	
 	public void close() {
 		// Guard
-		if (hasClosed)
+		if (hasClosed || playerInjection == null)
 			return;
-		
+
 		// Remove everything
 		for (PlayerInjector injection : playerInjection.values()) {
-			injection.cleanupAll();
+			if (injection != null) {
+				injection.cleanupAll();
+			}
 		}
-		
+
 		// Remove packet handlers
 		if (packetInjector != null)
 			packetInjector.cleanupAll();
 		
+		// Remove server handler
+		serverInjection.cleanupAll();
+		hasClosed = true;
+		
 		// Remove listeners
 		packetListeners.clear();
 		playerInjection.clear();
 		connectionLookup.clear();
-		hasClosed = true;
+		
+		// Clean up async handlers. We have to do this last.
+		asyncFilterManager.cleanupAll();
 	}
 	
 	@Override

ProtocolLib/src/com/comphenix/protocol/injector/PacketInjector.java

@@ -23,6 +23,7 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.bukkit.entity.Player;
 
@@ -52,6 +53,9 @@ class PacketInjector {
 	// Allows us to determine the sender
 	private Map<DataInputStream, Player> playerLookup;
 	
+	// Allows us to look up read packet injectors
+	private Map<Integer, ReadPacketModifier> readModifier;
+	
 	// Class loader
 	private ClassLoader classLoader;
 			
@@ -61,9 +65,24 @@ class PacketInjector {
 		this.classLoader = classLoader;
 		this.manager = manager;
 		this.playerLookup = playerLookup;
+		this.readModifier = new ConcurrentHashMap<Integer, ReadPacketModifier>();
 		initialize();
 	}
 	
+	/**
+	 * Undo a packet cancel.
+	 * @param id - the id of the packet.
+	 * @param packet - packet to uncancel.
+	 */
+	public void undoCancel(Integer id, Packet packet) {
+		ReadPacketModifier modifier = readModifier.get(id);
+		
+		// Cancelled packets are represented with NULL
+		if (modifier != null && modifier.getOverride(packet) == null) {
+			modifier.removeOverride(packet);
+		}
+	}
+	
 	private void initialize() throws IllegalAccessException {
 		if (intHashMap == null) {
 			// We're looking for the first static field with a Minecraft-object. This should be a IntHashMap.
@@ -109,10 +128,12 @@ class PacketInjector {
 		ex.setClassLoader(classLoader);
 		Class proxy = ex.createClass();
 		
+		// Create the proxy handler
+		ReadPacketModifier modifier = new ReadPacketModifier(packetID, this);
+		readModifier.put(packetID, modifier);
+		
 		// Add a static reference
-		Enhancer.registerStaticCallbacks(proxy, new Callback[] { 
-				new ReadPacketModifier(packetID, this) 
-		});
+		Enhancer.registerStaticCallbacks(proxy, new Callback[] { modifier });
 		
 		try {
 			// Override values
@@ -147,6 +168,7 @@ class PacketInjector {
 			
 			putMethod.invoke(intHashMap, packetID, old);
 			previous.remove(packetID);
+			readModifier.remove(packetID);
 			registry.remove(proxy);
 			overwritten.remove(packetID);
 			return true;

ProtocolLib/src/com/comphenix/protocol/injector/PlayerInjector.java

@@ -31,6 +31,7 @@ import org.bukkit.entity.Player;
 
 import com.comphenix.protocol.events.PacketContainer;
 import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.events.PacketListener;
 import com.comphenix.protocol.reflect.FieldUtils;
 import com.comphenix.protocol.reflect.FuzzyReflection;
 import com.comphenix.protocol.reflect.StructureModifier;
@@ -56,9 +57,11 @@ abstract class PlayerInjector {
 	
 	// Reference to the player's network manager
 	protected VolatileField networkManagerRef;
+	protected VolatileField serverHandlerRef;
 	protected Object networkManager;
 	
 	// Current net handler
+	protected Object serverHandler;
 	protected Object netHandler;
 	
 	// The packet manager and filters
@@ -75,12 +78,18 @@ abstract class PlayerInjector {
 		initialize();
 	}
 
+	/**
+	 * Retrieve the notch (NMS) entity player object.
+	 * @return Notch player object.
+	 */
+	protected EntityPlayer getEntityPlayer() {
+		CraftPlayer craft = (CraftPlayer) player;
+		return craft.getHandle();
+	}
+	
 	protected void initialize() throws IllegalAccessException {
 	
-		CraftPlayer craft = (CraftPlayer) player;
-		EntityPlayer notchEntity = craft.getHandle();
-		
-		Object serverHandler = null;
+		EntityPlayer notchEntity = getEntityPlayer();
 		
 		if (!hasInitialized) {
 			// Do this first, in case we encounter an exception
@@ -89,7 +98,8 @@ abstract class PlayerInjector {
 			// Retrieve the server handler
 			if (serverHandlerField == null)
 				serverHandlerField = FuzzyReflection.fromObject(notchEntity).getFieldByType(".*NetServerHandler");
-			serverHandler = FieldUtils.readField(serverHandlerField, notchEntity);
+			serverHandlerRef = new VolatileField(serverHandlerField, notchEntity);
+			serverHandler = serverHandlerRef.getValue();
 			
 			// Next, get the network manager 
 			if (networkManagerField == null) 
@@ -118,26 +128,31 @@ abstract class PlayerInjector {
 	 * @return Current net handler.
 	 * @throws IllegalAccessException Unable to find or retrieve net handler.
 	 */
-	private Object getNetHandler() throws IllegalAccessException {
+	protected Object getNetHandler() throws IllegalAccessException {
 		
 		// What a mess
 		try {
 			if (netHandlerField == null)
-				netHandlerField = FuzzyReflection.fromClass(networkManagerField.getType(), true).
+				netHandlerField = FuzzyReflection.fromClass(networkManager.getClass(), true).
 									getFieldByType("net\\.minecraft\\.NetHandler");
 		} catch (RuntimeException e1) {
+			// Swallow it
+		}
+		
+		// Second attempt
+		if (netHandlerField == null) {
 			try {
 				// Well, that sucks. Try just Minecraft objects then.
-				netHandlerField = FuzzyReflection.fromClass(networkManagerField.getType(), true).
+				netHandlerField = FuzzyReflection.fromClass(networkManager.getClass(), true).
 									 getFieldByType(FuzzyReflection.MINECRAFT_OBJECT);
 				
 			} catch (RuntimeException e2) {
-				return new IllegalAccessException("Cannot locate net handler. " + e2.getMessage());
+				throw new IllegalAccessException("Cannot locate net handler. " + e2.getMessage());
 			}
 		}
 		
 		// Get the handler
-		if (netHandler != null)
+		if (netHandler == null)
 			netHandler = FieldUtils.readField(netHandlerField, networkManager, true);
 		return netHandler;
 	}
@@ -190,6 +205,14 @@ abstract class PlayerInjector {
 	 */
 	public abstract void cleanupAll();
 	
+	/**
+	 * Invoked before a new listener is registered.
+	 * <p>
+	 * The player injector should throw an exception if this listener cannot be properly supplied with packet events. 
+	 * @param listener - the listener that is about to be registered.
+	 */
+	public abstract void checkListener(PacketListener listener);
+	
 	/**
 	 * Allows a packet to be recieved by the listeners.
 	 * @param packet - packet to recieve.
@@ -200,7 +223,7 @@ abstract class PlayerInjector {
 		Integer id = MinecraftRegistry.getPacketToID().get(packet.getClass());
 
 		// Make sure we're listening
-		if (sendingFilters.contains(id)) {	
+		if (id != null && sendingFilters.contains(id)) {
 			// A packet has been sent guys!
 			PacketContainer container = new PacketContainer(id, packet);
 			PacketEvent event = PacketEvent.fromServer(manager, container, player);

ProtocolLib/src/com/comphenix/protocol/injector/PrioritizedListener.java

@@ -0,0 +1,64 @@
+package com.comphenix.protocol.injector;
+
+import com.comphenix.protocol.events.ListenerPriority;
+import com.google.common.base.Objects;
+import com.google.common.primitives.Ints;
+
+/**
+ * Represents a listener with a priority.
+ * 
+ * @author Kristian
+ */
+public class PrioritizedListener<TListener> implements Comparable<PrioritizedListener<TListener>> {
+
+	private TListener listener;
+	private ListenerPriority priority;
+	
+	public PrioritizedListener(TListener listener, ListenerPriority priority) {
+		this.listener = listener;
+		this.priority = priority;
+	}
+
+	@Override
+	public int compareTo(PrioritizedListener<TListener> other) {
+		// This ensures that lower priority listeners are executed first
+		return Ints.compare(
+			this.getPriority().getSlot(),
+			other.getPriority().getSlot());
+	}
+	
+	// Note that this equals() method is NOT consistent with compareTo(). 
+	// But, it's a private class so who cares.
+	@SuppressWarnings("unchecked")
+	@Override
+	public boolean equals(Object obj) {
+		// We only care about the listener - priority itself should not make a difference
+	    if(obj instanceof PrioritizedListener){
+	        final PrioritizedListener<TListener> other = (PrioritizedListener<TListener>) obj;
+	        return Objects.equal(listener, other.listener);
+	    } else {
+	        return false;
+	    }
+	}
+	
+	@Override
+	public int hashCode() {
+		return Objects.hashCode(listener);
+	}
+	
+	/**
+	 * Retrieve the underlying listener.
+	 * @return Underlying listener.
+	 */
+	public TListener getListener() {
+		return listener;
+	}
+
+	/**
+	 * Retrieve the priority of this listener.
+	 * @return Listener priority.
+	 */
+	public ListenerPriority getPriority() {
+		return priority;
+	}
+}

ProtocolLib/src/com/comphenix/protocol/injector/ReadPacketModifier.java

@@ -45,6 +45,23 @@ class ReadPacketModifier implements MethodInterceptor {
 		this.packetID = packetID;
 		this.packetInjector = packetInjector;
 	}
+	
+	/**
+	 * Remove any packet overrides.
+	 * @param packet - the packet to rever
+	 */
+	public void removeOverride(Packet packet) {
+		override.remove(packet);
+	}
+	
+	/**
+	 * Retrieve the packet that overrides the methods of the given packet.
+	 * @param packet - the given packet.
+	 * @return Overriden object.
+	 */
+	public Object getOverride(Packet packet) {
+		return override.get(packet);
+	}
 
 	@Override
 	public Object intercept(Object thisObj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
@@ -60,9 +77,14 @@ class ReadPacketModifier implements MethodInterceptor {
 		if (override.containsKey(thisObj)) {
 			Object overridenObject = override.get(thisObj);
 			
-			// Cancel EVERYTHING, including "processPacket"
-			if (overridenObject == null)
-				return null;
+			// This packet has been cancelled
+			if (overridenObject == null) {
+				// So, cancel all void methods
+				if (method.getReturnType().equals(Void.TYPE))
+					return null;
+				else // Revert to normal for everything else
+					overridenObject = thisObj;
+			}
 			
 			returnValue = proxy.invokeSuper(overridenObject, args);
 		} else {
@@ -75,7 +97,7 @@ class ReadPacketModifier implements MethodInterceptor {
 			
 			// We need this in order to get the correct player
 			DataInputStream input = (DataInputStream) args[0];
-			
+
 			// Let the people know
 			PacketContainer container = new PacketContainer(packetID, (Packet) thisObj);
 			PacketEvent event = packetInjector.packetRecieved(container, input);

ProtocolLib/src/com/comphenix/protocol/injector/ReplacedArrayList.java

@@ -0,0 +1,136 @@
+package com.comphenix.protocol.injector;
+
+import java.util.Collection;
+import java.util.List;
+
+import com.google.common.base.Objects;
+import com.google.common.collect.BiMap;
+import com.google.common.collect.ForwardingList;
+import com.google.common.collect.HashBiMap;
+
+/**
+ * Represents an array list that wraps another list, while automatically replacing one element with another.
+ * <p>
+ * The replaced elements can be recovered. 
+ * 
+ * @author Kristian
+ * @param <TKey> - type of the elements we're replacing.
+ */
+class ReplacedArrayList<TKey> extends ForwardingList<TKey> {
+	private BiMap<TKey, TKey> replaceMap = HashBiMap.create();
+	private List<TKey> underlyingList;
+	
+	public ReplacedArrayList(List<TKey> underlyingList) {
+		this.underlyingList = underlyingList;
+	}
+	
+	@Override
+	public boolean add(TKey element) {
+		if (replaceMap.containsKey(element)) {
+			return super.add(replaceMap.get(element));
+		} else {
+			return super.add(element);
+		}
+	}
+	
+	@Override
+	public void add(int index, TKey element) {
+		if (replaceMap.containsKey(element)) {
+			super.add(index, replaceMap.get(element));
+		} else {
+			super.add(index, element);
+		}
+	}
+	
+	@Override
+	public boolean addAll(Collection<? extends TKey> collection) {
+		int oldSize = size();
+		
+		for (TKey element : collection)
+			add(element);
+		return size() != oldSize;
+	}
+	
+	@Override
+	public boolean addAll(int index, Collection<? extends TKey> elements) {
+		int oldSize = size();
+		
+		for (TKey element : elements)
+			add(index++, element);
+		return size() != oldSize;
+	}
+	
+	@Override
+	protected List<TKey> delegate() {
+		return underlyingList;
+	}
+
+	/**
+	 * Add a replace rule.
+	 * <p>
+	 * This automatically replaces every existing element.
+	 * @param target - instance to find.
+	 * @param replacement - instance to replace with.
+	 */
+	public synchronized void addMapping(TKey target, TKey replacement) {
+		replaceMap.put(target, replacement);
+
+		// Replace existing elements
+		replaceAll(target, replacement);
+	}
+	
+	/**
+	 * Revert the given mapping.
+	 * @param target - the instance we replaced.
+	 */
+	public synchronized void removeMapping(TKey target) {
+		// Make sure the mapping exist
+		if (replaceMap.containsKey(target)) {
+			TKey replacement = replaceMap.get(target);
+			replaceMap.remove(target);
+	
+			// Revert existing elements
+			replaceAll(replacement, target);
+		}
+	}
+	
+	/**
+	 * Replace all instances of the given object.
+	 * @param find - object to find.
+	 * @param replace - object to replace it with.
+	 */
+	public synchronized void replaceAll(TKey find, TKey replace) {
+		for (int i = 0; i < underlyingList.size(); i++) {
+			if (Objects.equal(underlyingList.get(i), find))
+				underlyingList.set(i, replace);
+		}
+	}
+	
+	/**
+	 * Undo all replacements.
+	 */
+	public synchronized void revertAll() {
+		
+		// No need to do anything else
+		if (replaceMap.size() < 1)
+			return;
+		
+		BiMap<TKey, TKey> inverse = replaceMap.inverse();
+		
+		for (int i = 0; i < underlyingList.size(); i++) {
+			TKey replaced = underlyingList.get(i);
+			
+			if (inverse.containsKey(replaced)) {
+				underlyingList.set(i, inverse.get(replaced));
+			}
+		}
+		
+		replaceMap.clear();
+	}
+	
+	@Override
+	protected void finalize() throws Throwable {
+		revertAll();
+		super.finalize();
+	}
+}

ProtocolLib/src/com/comphenix/protocol/injector/SortedPacketListenerList.java

@@ -0,0 +1,66 @@
+package com.comphenix.protocol.injector;
+
+import java.util.Collection;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import com.comphenix.protocol.concurrency.AbstractConcurrentListenerMultimap;
+import com.comphenix.protocol.events.PacketAdapter;
+import com.comphenix.protocol.events.PacketEvent;
+import com.comphenix.protocol.events.PacketListener;
+
+/**
+ * Registry of synchronous packet listeners.
+ * 
+ * @author Kristian
+ */
+class SortedPacketListenerList extends AbstractConcurrentListenerMultimap<PacketListener> {
+	
+	/**
+	 * Invokes the given packet event for every registered listener.
+	 * @param logger - the logger that will be used to inform about listener exceptions.
+	 * @param event - the packet event to invoke.
+	 */
+	public void invokePacketRecieving(Logger logger, PacketEvent event) {
+		Collection<PrioritizedListener<PacketListener>> list = getListener(event.getPacketID());
+		
+		if (list == null)
+			return;
+
+		// The returned list is thread-safe
+		for (PrioritizedListener<PacketListener> element : list) {
+			try {
+				element.getListener().onPacketReceiving(event);
+			} catch (Throwable e) {
+				// Minecraft doesn't want your Exception.
+				logger.log(Level.SEVERE, 
+						"Exception occured in onPacketReceiving() for " + 
+							PacketAdapter.getPluginName(element.getListener()), e);
+			}
+		}
+	}
+	
+	/**
+	 * Invokes the given packet event for every registered listener.
+	 * @param logger - the logger that will be used to inform about listener exceptions.
+	 * @param event - the packet event to invoke.
+	 */
+	public void invokePacketSending(Logger logger, PacketEvent event) {
+		Collection<PrioritizedListener<PacketListener>> list = getListener(event.getPacketID());
+		
+		if (list == null)
+			return;
+		
+		for (PrioritizedListener<PacketListener> element : list) {
+			try {
+				element.getListener().onPacketSending(event);
+			} catch (Throwable e) {
+				// Minecraft doesn't want your Exception.
+				logger.log(Level.SEVERE, 
+						"Exception occured in onPacketSending() for " + 
+							PacketAdapter.getPluginName(element.getListener()), e);
+			}
+		}
+	}
+	
+}

ProtocolLib/src/com/comphenix/protocol/injector/StructureCache.java

@@ -17,12 +17,17 @@
 
 package com.comphenix.protocol.injector;
 
-import java.util.HashMap;
-import java.util.Map;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 
 import net.minecraft.server.Packet;
 
 import com.comphenix.protocol.reflect.StructureModifier;
+import com.comphenix.protocol.reflect.compiler.BackgroundCompiler;
+import com.comphenix.protocol.reflect.compiler.CompileListener;
+import com.comphenix.protocol.reflect.compiler.CompiledStructureModifier;
 
 /**
  * Caches structure modifiers.
@@ -30,7 +35,10 @@ import com.comphenix.protocol.reflect.StructureModifier;
  */
 public class StructureCache {
 	// Structure modifiers
-	private static Map<Integer, StructureModifier<Object>> structureModifiers = new HashMap<Integer, StructureModifier<Object>>();
+	private static ConcurrentMap<Integer, StructureModifier<Object>> structureModifiers = 
+			new ConcurrentHashMap<Integer, StructureModifier<Object>>();
+	
+	private static Set<Integer> compiling = new HashSet<Integer>();
 	
 	/**
 	 * Creates an empty Minecraft packet of the given ID.
@@ -53,15 +61,51 @@ public class StructureCache {
 	 * @return A structure modifier.
 	 */
 	public static StructureModifier<Object> getStructure(int id) {
+		// Compile structures by default
+		return getStructure(id, true);
+	}
+	
+	/**
+	 * Retrieve a cached structure modifier for the given packet id.
+	 * @param id - packet ID.
+	 * @param compile - whether or not to asynchronously compile the structure modifier.
+	 * @return A structure modifier.
+	 */
+	public static StructureModifier<Object> getStructure(int id, boolean compile) {
 		
 		StructureModifier<Object> result = structureModifiers.get(id);
-		
-		// Use the vanilla class definition
+
+		// We don't want to create this for every lookup
 		if (result == null) {
-			result = new StructureModifier<Object>(
+			// Use the vanilla class definition
+			final StructureModifier<Object> value = new StructureModifier<Object>(
 					MinecraftRegistry.getPacketClassFromID(id, true), Packet.class, true);
 			
-			structureModifiers.put(id, result);
+			result = structureModifiers.putIfAbsent(id, value);
+			
+			// We may end up creating multiple modifiers, but we'll agree on which to use
+			if (result == null) {
+				result = value;
+			}
+		}
+		
+		// Automatically compile the structure modifier
+		if (compile && !(result instanceof CompiledStructureModifier)) {
+			// Compilation is many orders of magnitude slower than synchronization
+			synchronized (compiling) {
+				final int idCopy = id;
+				final BackgroundCompiler compiler = BackgroundCompiler.getInstance();
+				
+				if (!compiling.contains(id) && compiler != null) {
+					compiler.scheduleCompilation(result, new CompileListener<Object>() {
+						@Override
+						public void onCompiled(StructureModifier<Object> compiledModifier) {
+							structureModifiers.put(idCopy, compiledModifier);
+						}
+					});
+					compiling.add(id);
+				}
+			}
 		}
 		
 		return result;

ProtocolLib/src/com/comphenix/protocol/reflect/FuzzyReflection.java

@@ -19,8 +19,10 @@ package com.comphenix.protocol.reflect;
 
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.LinkedHashSet;
+import java.util.List;
 import java.util.Set;
 import java.util.regex.Pattern;
 
@@ -96,6 +98,7 @@ public class FuzzyReflection {
 	 * Retrieves a method by looking at its name.
 	 * @param nameRegex -  regular expression that will match method names.
 	 * @return The first method that satisfies the regular expression.
+	 * @throws RuntimeException If the method cannot be found.
 	 */
 	public Method getMethodByName(String nameRegex) {
 		
@@ -139,11 +142,38 @@ public class FuzzyReflection {
 	 * @return The first method that satisfies the parameter types.
 	 */
 	public Method getMethodByParameters(String name, Class<?> returnType, Class<?>[] args) {
+		// Find the correct method to call
+		List<Method> methods = getMethodListByParameters(returnType, args);
+		
+		if (methods.size() > 0) {
+			return methods.get(0);
+		} else {
+			// That sucks
+			throw new RuntimeException("Unable to find " + name + " in " + source.getName());
+		}
+	}
 	
+	/**
+	 * Retrieves a method by looking at the parameter types and return type only.
+	 * @param name - potential name of the method. Only used by the error mechanism.
+	 * @param returnType - regular expression matching the return type of the method to find.
+	 * @param args - regular expressions of the matching parameter types.
+	 * @return The first method that satisfies the parameter types.
+	 */
+	public Method getMethodByParameters(String name, String returnTypeRegex, String[] argsRegex) {
+	
+		Pattern match = Pattern.compile(returnTypeRegex);
+		Pattern[] argMatch = new Pattern[argsRegex.length];
+		
+		for (int i = 0; i < argsRegex.length; i++) {
+			argMatch[i] = Pattern.compile(argsRegex[i]);
+		}
+		
 		// Find the correct method to call
 		for (Method method : getMethods()) {
-			if (method.getReturnType().equals(returnType) && Arrays.equals(method.getParameterTypes(), args)) {
-				return method;
+			if (match.matcher(method.getReturnType().getName()).matches()) {
+				if (matchParameters(argMatch, method.getParameterTypes()))
+					return method;
 			}
 		}
 		
@@ -151,6 +181,39 @@ public class FuzzyReflection {
 		throw new RuntimeException("Unable to find " + name + " in " + source.getName());
 	}
 	
+	private boolean matchParameters(Pattern[] parameterMatchers, Class<?>[] argTypes) {
+		if (parameterMatchers.length != argTypes.length)
+			throw new IllegalArgumentException("Arrays must have the same cardinality.");
+		
+		// Check types against the regular expressions
+		for (int i = 0; i < argTypes.length; i++) {
+			if (!parameterMatchers[i].matcher(argTypes[i].getName()).matches())
+				return false;
+		}
+		
+		return true;
+	}
+	
+	/**
+	 * Retrieves every method that has the given parameter types and return type.
+	 * @param returnType - return type of the method to find.
+	 * @param args - parameter types of the method to find.
+	 * @return Every method that satisfies the given constraints.
+	 */
+	public List<Method> getMethodListByParameters(Class<?> returnType, Class<?>[] args) {
+	
+		List<Method> methods = new ArrayList<Method>();
+		
+		// Find the correct method to call
+		for (Method method : getMethods()) {
+			if (method.getReturnType().equals(returnType) && Arrays.equals(method.getParameterTypes(), args)) {
+				methods.add(method);
+			}
+		}
+		
+		return methods;
+	}
+	
 	/**
 	 * Retrieves a field by name.
 	 * @param nameRegex - regular expression that will match a field name.
@@ -172,6 +235,46 @@ public class FuzzyReflection {
 									nameRegex + " in " + source.getName());
 	}
 	
+	/**
+	 * Retrieves the first field with a type equal to or more specific to the given type.
+	 * @param name - name the field probably is given. This will only be used in the error message.
+	 * @param type - type of the field to find.
+	 * @return The first field with a type that is an instance of the given type.
+	 */
+	public Field getFieldByType(String name, Class<?> type) {
+		
+		List<Field> fields = getFieldListByType(type);
+		
+		if (fields.size() > 0) {
+			return fields.get(0);
+		} else {
+			// Looks like we're outdated. Too bad.
+			throw new RuntimeException(String.format("Unable to find a field %s with the type %s in %s",
+					name, type.getName(), source.getName())
+			);
+		}
+	}
+	
+	/**
+	 * Retrieves every field with a type equal to or more specific to the given type.
+	 * @param type - type of the fields to find.
+	 * @return Every field with a type that is an instance of the given type.
+	 */
+	public List<Field> getFieldListByType(Class<?> type) {
+		
+		List<Field> fields = new ArrayList<Field>();
+		
+		// Field with a compatible type
+		for (Field field : getFields()) {
+			// A assignable from B -> B instanceOf A
+			if (type.isAssignableFrom(field.getType())) {
+				fields.add(field);
+			}
+		}
+		
+		return fields;
+	}
+	
 	/**
 	 * Retrieves a field by type.
 	 * <p>

ProtocolLib/src/com/comphenix/protocol/reflect/StructureModifier.java

@@ -21,34 +21,45 @@ import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 import java.util.ArrayList;
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
+import com.comphenix.protocol.reflect.compiler.BackgroundCompiler;
 import com.comphenix.protocol.reflect.instances.DefaultInstances;
 import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 
+/**
+ * Provides list-oriented access to the fields of a Minecraft packet.
+ * <p>
+ * Implemented by using reflection. Use a CompiledStructureModifier, if speed is essential.
+ * 
+ * @author Kristian
+ * @param <TField> Type of the fields to retrieve.
+ */
 @SuppressWarnings("rawtypes")
 public class StructureModifier<TField> {
 	
 	// Object and its type
-	private Class targetType;
-	private Object target;
+	protected Class targetType;
+	protected Object target;
 	
 	// Converter. May be NULL.
-	private EquivalentConverter<TField> converter;
+	protected EquivalentConverter<TField> converter;
 	
 	// The fields to read in order
-	private Class fieldType;
-	private List<Field> data = new ArrayList<Field>();
+	protected Class fieldType;
+	protected List<Field> data = new ArrayList<Field>();
 	
 	// Improved default values
-	private Set<Field> defaultFields;
+	protected Map<Field, Integer> defaultFields;
 	
 	// Cache of previous types
-	private Map<Class, StructureModifier> subtypeCache;
+	protected Map<Class, StructureModifier> subtypeCache;
+	
+	// Whether or subclasses should handle conversion
+	protected boolean customConvertHandling;
 	
 	/**
 	 * Creates a structure modifier.
@@ -58,22 +69,38 @@ public class StructureModifier<TField> {
 	 */
 	public StructureModifier(Class targetType, Class superclassExclude, boolean requireDefault) {
 		List<Field> fields = getFields(targetType, superclassExclude);
-		Set<Field> defaults = requireDefault ? generateDefaultFields(fields) : new HashSet<Field>();
+		Map<Field, Integer> defaults = requireDefault ? generateDefaultFields(fields) : new HashMap<Field, Integer>();
 		
-		initialize(targetType, Object.class, fields, defaults, null, new HashMap<Class, StructureModifier>());
+		initialize(targetType, Object.class, fields, defaults, null, new ConcurrentHashMap<Class, StructureModifier>());
 	}
 	
-	private StructureModifier(StructureModifier<TField> other, Object target) {
-		initialize(other.targetType, other.fieldType, other.data, other.defaultFields, other.converter, other.subtypeCache);
-		this.target = target;
+	/**
+	 * Consumers of this method should call "initialize".
+	 */
+	protected StructureModifier() {
+		
 	}
 	
-	private StructureModifier() {
-		// Consumers of this method should call "initialize"
+	/**
+	 * Initialize using the same field types.
+	 * @param other - information to set.
+	 */
+	protected void initialize(StructureModifier<TField> other) {
+		initialize(other.targetType, other.fieldType, other.data, 
+				   other.defaultFields, other.converter, other.subtypeCache);
 	}
 	
-	private void initialize(Class targetType, Class fieldType, 
-			  List<Field> data, Set<Field> defaultFields,
+	/**
+	 * Initialize every field of this class.
+	 * @param targetType - type of the object we're reading and writing from.
+	 * @param fieldType - the common type of the fields we're modifying.
+	 * @param data - list of fields to modify.
+	 * @param defaultFields - list of fields that will be automatically initialized.
+	 * @param converter - converts between the common field type and the actual type the consumer expects.
+	 * @param subTypeCache - a structure modifier cache.
+	 */
+	protected void initialize(Class targetType, Class fieldType, 
+			  List<Field> data, Map<Field, Integer> defaultFields,
 			  EquivalentConverter<TField> converter, Map<Class, StructureModifier> subTypeCache) {
 		this.targetType = targetType;
 		this.fieldType = fieldType;
@@ -101,7 +128,7 @@ public class StructureModifier<TField> {
 			Object result = FieldUtils.readField(data.get(fieldIndex), target, true);
 			
 			// Use the converter, if we have it
-			if (converter != null)
+			if (needConversion())
 				return converter.getSpecific(result);
 			else
 				return (TField) result;
@@ -140,7 +167,7 @@ public class StructureModifier<TField> {
 			throw new IllegalStateException("Cannot write to a NULL target.");
 		
 		// Use the converter, if it exists
-		Object obj = converter != null ? converter.getGeneric(value) : value;
+		Object obj = needConversion() ? converter.getGeneric(value) : value;
 		
 		try {
 			FieldUtils.writeField(data.get(fieldIndex), target, obj, true);
@@ -152,6 +179,14 @@ public class StructureModifier<TField> {
 		return this;
 	}
 	
+	/**
+	 * Whether or not we should use the converter instance.
+	 * @return TRUE if we should, FALSE otherwise.
+	 */
+	private final boolean needConversion() {
+		return converter != null && !customConvertHandling;
+	}
+	
 	/**
 	 * Writes the value of a given field IF and ONLY if it exists.
 	 * @param fieldIndex - index of the potential field.
@@ -197,7 +232,7 @@ public class StructureModifier<TField> {
 		DefaultInstances generator = DefaultInstances.DEFAULT;
 		
 		// Write a default instance to every field
-		for (Field field : defaultFields) {
+		for (Field field : defaultFields.keySet()) {
 			try {
 				FieldUtils.writeField(field, target, 
 						generator.getDefault(field.getType()), true);
@@ -223,24 +258,32 @@ public class StructureModifier<TField> {
 		// Do we need to update the cache?
 		if (result == null) {
 			List<Field> filtered = new ArrayList<Field>();
-			Set<Field> defaults = new HashSet<Field>();
+			Map<Field, Integer> defaults = new HashMap<Field, Integer>();
+			int index = 0;
 			
 			for (Field field : data) {
 				if (fieldType != null && fieldType.isAssignableFrom(field.getType())) {
 					filtered.add(field);
 					
-					if (defaultFields.contains(field))
-						defaults.add(field);
+					// Don't use the original index
+					if (defaultFields.containsKey(field))
+						defaults.put(field, index);
 				}
+				
+				// Keep track of the field index
+				index++;
 			}
 			
 			// Cache structure modifiers
-			result = new StructureModifier<T>();
-			result.initialize(targetType, fieldType, filtered, defaults, 
-							  converter, new HashMap<Class, StructureModifier>());
+			result = withFieldType(fieldType, filtered, defaults, converter);
 			
-			if (fieldType != null)
+			if (fieldType != null) {
 				subtypeCache.put(fieldType, result);
+				
+				// Automatically compile the structure modifier
+				if (BackgroundCompiler.getInstance() != null) 
+					BackgroundCompiler.getInstance().scheduleCompilation(subtypeCache, fieldType);
+			}
 		}
 		
 		// Add the target too
@@ -296,28 +339,59 @@ public class StructureModifier<TField> {
 		return data.size();
 	}
 	
+	/**
+	 * Create a new structure modifier for the new field type.
+	 * @param fieldType - common type of each field.
+	 * @param filtered - list of fields after filtering the original modifier.
+	 * @param defaults - list of default values after filtering the original.
+	 * @param converter - the new converter.
+	 * @return A new structure modifier.
+	 */
+	protected <T> StructureModifier<T> withFieldType(
+			Class fieldType, List<Field> filtered, 
+			Map<Field, Integer> defaults, EquivalentConverter<T> converter) {
+		
+		StructureModifier<T> result = new StructureModifier<T>();
+		result.initialize(targetType, fieldType, filtered, defaults, 
+						  converter, new ConcurrentHashMap<Class, StructureModifier>());
+		return result;
+	}
+	
 	/**
 	 * Retrieves a structure modifier of the same type for a different object target.
 	 * @param target - different target of the same type.
 	 * @return Structure modifier with the new target.
 	 */
 	public StructureModifier<TField> withTarget(Object target) {
-		return new StructureModifier<TField>(this, target);
+		StructureModifier<TField> copy = new StructureModifier<TField>();
+		
+		// Create a new instance
+		copy.initialize(targetType, fieldType, data, defaultFields, converter, subtypeCache);
+		copy.target = target;
+		return copy;
 	}
 	
 	/**
 	 * Retrieves a structure modifier with the same type and target, but using a new object converter.
-	 * @param converter- the object converter to use.
+	 * @param converter - the object converter to use.
 	 * @return Structure modifier with the new converter.
 	 */
 	@SuppressWarnings("unchecked")
 	private <T> StructureModifier<T> withConverter(EquivalentConverter<T> converter) {
-		StructureModifier copy = new StructureModifier(this, target);
+		StructureModifier copy = withTarget(target);
 		
-		copy.converter = converter;
+		copy.setConverter(converter);
 		return copy;
 	}
 	
+	/**
+	 * Set the current object converter. Should only be called during construction.
+	 * @param converter - current object converter.
+	 */
+	protected void setConverter(EquivalentConverter<TField> converter) {
+		this.converter = converter;
+	}
+	
 	/**
 	 * Retrieves a list of the fields matching the constraints of this structure modifier.
 	 * @return List of fields.
@@ -325,7 +399,7 @@ public class StructureModifier<TField> {
 	public List<Field> getFields() {
 		return ImmutableList.copyOf(data);
 	}
-	
+
 	/**
 	 * Retrieve every value stored in the fields of the current type.
 	 * @return Every field value.
@@ -334,17 +408,19 @@ public class StructureModifier<TField> {
 	public List<TField> getValues() throws FieldAccessException {
 		List<TField> values = new ArrayList<TField>();
 		
-		for (int i = 0; i < size(); i++)
+		for (int i = 0; i < size(); i++) {
 			values.add(read(i));
+		}
 		
 		return values;
 	}
 	
 	// Used to generate plausible default values
-	private static Set<Field> generateDefaultFields(List<Field> fields) {
+	private static Map<Field, Integer> generateDefaultFields(List<Field> fields) {
 		
-		Set<Field> requireDefaults = new HashSet<Field>();
+		Map<Field, Integer> requireDefaults = new HashMap<Field, Integer>();
 		DefaultInstances generator = DefaultInstances.DEFAULT;
+		int index = 0;
 		
 		for (Field field : fields) {
 			Class<?> type = field.getType();
@@ -354,9 +430,12 @@ public class StructureModifier<TField> {
 				// Next, see if we actually can generate a default value
 				if (generator.getDefault(type) != null) {
 					// If so, require it
-					requireDefaults.add(field);
+					requireDefaults.put(field, index);
 				}
 			}
+			
+			// Increment field index
+			index++;
 		}
 		
 		return requireDefaults;

ProtocolLib/src/com/comphenix/protocol/reflect/VolatileField.java

@@ -155,6 +155,13 @@ public class VolatileField {
 		}
 	}
 	
+	/**
+	 * Determine whether or not we'll need to revert the value.
+	 */
+	public boolean isCurrentSet() {
+		return currentSet;
+	}
+	
 	private void ensureLoaded() {
 		// Load the value if we haven't already
 		if (!previousLoaded) {

ProtocolLib/src/com/comphenix/protocol/reflect/compiler/BackgroundCompiler.java

@@ -0,0 +1,183 @@
+package com.comphenix.protocol.reflect.compiler;
+
+import java.util.Map;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import com.comphenix.protocol.reflect.StructureModifier;
+
+/**
+ * Compiles structure modifiers on a background thread.
+ * <p>
+ * This is necessary as we cannot block the main thread.
+ * 
+ * @author Kristian
+ */
+public class BackgroundCompiler {
+
+	// How long to wait for a shutdown
+	public static final int SHUTDOWN_DELAY_MS = 2000;
+	
+	// The single background compiler we're using
+	private static BackgroundCompiler backgroundCompiler;
+	
+	private StructureCompiler compiler;
+	private boolean enabled;
+	private boolean shuttingDown;
+	
+	private ExecutorService executor;
+	
+	/**
+	 * Retrieves the current background compiler.
+	 * @return Current background compiler.
+	 */
+	public static BackgroundCompiler getInstance() {
+		return backgroundCompiler;
+	}
+	
+	/**
+	 * Sets the single background compiler we're using.
+	 * @param backgroundCompiler - current background compiler, or NULL if the library is not loaded.
+	 */
+	public static void setInstance(BackgroundCompiler backgroundCompiler) {
+		BackgroundCompiler.backgroundCompiler = backgroundCompiler;
+	}
+	
+	/**
+	 * Initialize a background compiler.
+	 * @param loader - class loader from Bukkit.
+	 */
+	public BackgroundCompiler(ClassLoader loader) {
+		this(loader, Executors.newSingleThreadExecutor());
+	}
+
+	/**
+	 * Initialize a background compiler utilizing the given thread pool.
+	 * @param loader - class loader from Bukkit.
+	 * @param executor - thread pool we'll use.
+	 */
+	public BackgroundCompiler(ClassLoader loader, ExecutorService executor) {
+		if (loader == null)
+			throw new IllegalArgumentException("loader cannot be NULL");
+		if (executor == null)
+			throw new IllegalArgumentException("executor cannot be NULL");
+		
+		this.compiler = new StructureCompiler(loader);
+		this.executor = executor;
+		this.enabled = true;
+	}
+	
+	/**
+	 * Ensure that the indirectly given structure modifier is eventually compiled.
+	 * @param cache - store of structure modifiers.
+	 * @param key - key of the structure modifier to compile.
+	 */
+	@SuppressWarnings("rawtypes")
+	public void scheduleCompilation(final Map<Class, StructureModifier> cache, final Class key) {
+		
+		@SuppressWarnings("unchecked")
+		final StructureModifier<Object> uncompiled = cache.get(key);
+		
+		if (uncompiled != null) {
+			scheduleCompilation(uncompiled, new CompileListener<Object>() {
+				@Override
+				public void onCompiled(StructureModifier<Object> compiledModifier) {
+					// Update cache
+					cache.put(key, compiledModifier);
+				}
+			});
+		}
+	}
+	
+	/**
+	 * Ensure that the given structure modifier is eventually compiled.
+	 * @param uncompiled - structure modifier to compile.
+	 * @param listener - listener responsible for responding to the compilation.
+	 */
+	public <TKey> void scheduleCompilation(final StructureModifier<TKey> uncompiled, final CompileListener<TKey> listener) {
+
+		// Only schedule if we're enabled
+		if (enabled && !shuttingDown) {
+			
+			// Don't try to schedule anything
+			if (executor == null || executor.isShutdown())
+				return;
+			
+			try {
+				executor.submit(new Callable<Object>() {
+					@Override
+					public Object call() throws Exception {
+		
+						StructureModifier<TKey> modifier = uncompiled;
+						
+						// Do our compilation
+						modifier = compiler.compile(modifier);
+						listener.onCompiled(modifier);
+						
+						// We'll also return the new structure modifier
+						return modifier;
+					}
+				});
+			} catch (RejectedExecutionException e) {
+				// Occures when the underlying queue is overflowing. Since the compilation  
+				// is only an optmization and not really essential we'll just log this failure 
+				// and move on.
+				Logger.getLogger("Minecraft").log(Level.WARNING, "Unable to schedule compilation task.", e);
+			}
+		}
+	}
+	
+	/**
+	 * Clean up after ourselves using the default timeout.
+	 */
+	public void shutdownAll() {
+		shutdownAll(SHUTDOWN_DELAY_MS, TimeUnit.MILLISECONDS);
+	}
+	
+	/**
+	 * Clean up after ourselves.
+	 * @param timeout - the maximum time to wait.
+	 * @param unit - the time unit of the timeout argument.
+	 */
+	public void shutdownAll(long timeout, TimeUnit unit) {
+		setEnabled(false);
+		shuttingDown = true;
+		executor.shutdown();
+		
+		try {
+			executor.awaitTermination(timeout, unit);
+		} catch (InterruptedException e) {
+			// Unlikely to ever occur.
+			e.printStackTrace();
+		}
+	}
+	
+	/**
+	 * Retrieve whether or not the background compiler is enabled.
+	 * @return TRUE if it is enabled, FALSE otherwise.
+	 */
+	public boolean isEnabled() {
+		return enabled;
+	}
+
+	/**
+	 * Sets whether or not the background compiler is enabled.
+	 * @param enabled - TRUE to enable it, FALSE otherwise.
+	 */
+	public void setEnabled(boolean enabled) {
+		this.enabled = enabled;
+	}
+
+	/**
+	 * Retrieve the current structure compiler.
+	 * @return Current structure compiler.
+	 */
+	public StructureCompiler getCompiler() {
+		return compiler;
+	}
+}

ProtocolLib/src/com/comphenix/protocol/reflect/compiler/BoxingHelper.java

@@ -0,0 +1,275 @@
+package com.comphenix.protocol.reflect.compiler;
+
+import net.sf.cglib.asm.*;
+
+/**
+ * Used by the compiler to automatically box and unbox values.
+ */
+class BoxingHelper {
+
+	private final static Type BYTE_TYPE = Type.getObjectType("java/lang/Byte");
+	private final static Type BOOLEAN_TYPE = Type.getObjectType("java/lang/Boolean");
+	private final static Type SHORT_TYPE = Type.getObjectType("java/lang/Short");
+	private final static Type CHARACTER_TYPE = Type.getObjectType("java/lang/Character");
+	private final static Type INTEGER_TYPE = Type.getObjectType("java/lang/Integer");
+	private final static Type FLOAT_TYPE = Type.getObjectType("java/lang/Float");
+	private final static Type LONG_TYPE = Type.getObjectType("java/lang/Long");
+	private final static Type DOUBLE_TYPE = Type.getObjectType("java/lang/Double");
+	private final static Type NUMBER_TYPE = Type.getObjectType("java/lang/Number");
+	private final static Type OBJECT_TYPE = Type.getObjectType("java/lang/Object");
+
+	private final static MethodDescriptor BOOLEAN_VALUE = MethodDescriptor.getMethod("boolean booleanValue()");
+	private final static MethodDescriptor CHAR_VALUE = MethodDescriptor.getMethod("char charValue()");
+	private final static MethodDescriptor INT_VALUE = MethodDescriptor.getMethod("int intValue()");
+	private final static MethodDescriptor FLOAT_VALUE = MethodDescriptor.getMethod("float floatValue()");
+	private final static MethodDescriptor LONG_VALUE = MethodDescriptor.getMethod("long longValue()");
+	private final static MethodDescriptor DOUBLE_VALUE = MethodDescriptor.getMethod("double doubleValue()");
+
+	private MethodVisitor mv;
+	
+	public BoxingHelper(MethodVisitor mv) {
+		this.mv = mv;
+	}
+	
+	/**
+	 * Generates the instructions to box the top stack value. This value is
+	 * replaced by its boxed equivalent on top of the stack.
+	 *
+	 * @param type the type of the top stack value.
+	 */
+	public void box(final Type type){
+		if(type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
+			return;
+		}
+		
+		if(type == Type.VOID_TYPE) {
+			push((String) null);
+		} else {
+			Type boxed = type;
+			
+			switch(type.getSort()) {
+				case Type.BYTE:
+					boxed = BYTE_TYPE;
+					break;
+				case Type.BOOLEAN:
+					boxed = BOOLEAN_TYPE;
+					break;
+				case Type.SHORT:
+					boxed = SHORT_TYPE;
+					break;
+				case Type.CHAR:
+					boxed = CHARACTER_TYPE;
+					break;
+				case Type.INT:
+					boxed = INTEGER_TYPE;
+					break;
+				case Type.FLOAT:
+					boxed = FLOAT_TYPE;
+					break;
+				case Type.LONG:
+					boxed = LONG_TYPE;
+					break;
+				case Type.DOUBLE:
+					boxed = DOUBLE_TYPE;
+					break;
+			}
+			
+			newInstance(boxed);
+			if(type.getSize() == 2) {
+				// Pp -> Ppo -> oPpo -> ooPpo -> ooPp -> o
+				dupX2();
+				dupX2();
+				pop();
+			} else {
+				// p -> po -> opo -> oop -> o
+				dupX1();
+				swap();
+			}
+			
+			invokeConstructor(boxed, new MethodDescriptor("<init>", Type.VOID_TYPE, new Type[] {type}));
+		}
+	}
+	
+	/**
+	 * Generates the instruction to invoke a constructor.
+	 *
+	 * @param type   the class in which the constructor is defined.
+	 * @param method the constructor to be invoked.
+	 */
+	public void invokeConstructor(final Type type, final MethodDescriptor method){
+		invokeInsn(Opcodes.INVOKESPECIAL, type, method);
+	}
+	
+	/**
+	 * Generates a DUP_X1 instruction.
+	 */
+	public void dupX1(){
+		mv.visitInsn(Opcodes.DUP_X1);
+	}
+
+	/**
+	 * Generates a DUP_X2 instruction.
+	 */
+	public void dupX2(){
+		mv.visitInsn(Opcodes.DUP_X2);
+	}
+	
+	/**
+	 * Generates a POP instruction.
+	 */
+	public void pop(){
+		mv.visitInsn(Opcodes.POP);
+	}
+
+	/**
+	 * Generates a SWAP instruction.
+	 */
+	public void swap(){
+		mv.visitInsn(Opcodes.SWAP);
+	}
+	
+	/**
+	 * Generates the instruction to push the given value on the stack.
+	 *
+	 * @param value the value to be pushed on the stack.
+	 */
+	public void push(final boolean value){
+		push(value ? 1 : 0);
+	}
+	
+	/**
+	 * Generates the instruction to push the given value on the stack.
+	 * 
+	 * @param value the value to be pushed on the stack.
+	 */
+	public void push(final int value) {
+		if (value >= -1 && value <= 5) {
+			mv.visitInsn(Opcodes.ICONST_0 + value);
+		} else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
+			mv.visitIntInsn(Opcodes.BIPUSH, value);
+		} else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
+			mv.visitIntInsn(Opcodes.SIPUSH, value);
+		} else {
+			mv.visitLdcInsn(new Integer(value));
+		}
+	}
+
+	/**
+	 * Generates the instruction to create a new object.
+	 *
+	 * @param type the class of the object to be created.
+	 */
+	public void newInstance(final Type type){
+		typeInsn(Opcodes.NEW, type);
+	}
+	
+	/**
+	 * Generates the instruction to push the given value on the stack.
+	 * 
+	 * @param value the value to be pushed on the stack. May be <tt>null</tt>.
+	 */
+	public void push(final String value) {
+		if (value == null) {
+			mv.visitInsn(Opcodes.ACONST_NULL);
+		} else {
+			mv.visitLdcInsn(value);
+		}
+	}
+
+	/**
+	 * Generates the instructions to unbox the top stack value. This value is
+	 * replaced by its unboxed equivalent on top of the stack.
+	 * 
+	 * @param type
+	 *            the type of the top stack value.
+	 */
+	public void unbox(final Type type){
+		Type t = NUMBER_TYPE;
+		MethodDescriptor sig = null;
+		
+		switch(type.getSort()) {
+			case Type.VOID:
+				return;
+			case Type.CHAR:
+				t = CHARACTER_TYPE;
+				sig = CHAR_VALUE;
+				break;
+			case Type.BOOLEAN:
+				t = BOOLEAN_TYPE;
+				sig = BOOLEAN_VALUE;
+				break;
+			case Type.DOUBLE:
+				sig = DOUBLE_VALUE;
+				break;
+			case Type.FLOAT:
+				sig = FLOAT_VALUE;
+				break;
+			case Type.LONG:
+				sig = LONG_VALUE;
+				break;
+			case Type.INT:
+			case Type.SHORT:
+			case Type.BYTE:
+				sig = INT_VALUE;
+			}
+		
+		if(sig == null) {
+			checkCast(type);
+		} else {
+			checkCast(t);
+			invokeVirtual(t, sig);
+		}
+	}
+
+	/**
+	 * Generates the instruction to check that the top stack value is of the
+	 * given type.
+	 *
+	 * @param type a class or interface type.
+	 */
+	public void checkCast(final Type type){
+		if(!type.equals(OBJECT_TYPE)) {
+			typeInsn(Opcodes.CHECKCAST, type);
+		}
+	}
+	
+	/**
+	 * Generates the instruction to invoke a normal method.
+	 *
+	 * @param owner  the class in which the method is defined.
+	 * @param method the method to be invoked.
+	 */
+	public void invokeVirtual(final Type owner, final MethodDescriptor method){
+		invokeInsn(Opcodes.INVOKEVIRTUAL, owner, method);
+	}
+	
+	/**
+	 * Generates an invoke method instruction.
+	 *
+	 * @param opcode the instruction's opcode.
+	 * @param type   the class in which the method is defined.
+	 * @param method the method to be invoked.
+	 */
+	private void invokeInsn(final int opcode, final Type type, final MethodDescriptor method){
+		String owner = type.getSort() == Type.ARRAY ? type.getDescriptor() : type.getInternalName();
+		mv.visitMethodInsn(opcode, owner, method.getName(), method.getDescriptor());
+	}
+	
+	/**
+	 * Generates a type dependent instruction.
+	 *
+	 * @param opcode the instruction's opcode.
+	 * @param type   the instruction's operand.
+	 */
+	private void typeInsn(final int opcode, final Type type){
+		String desc;
+		
+		if(type.getSort() == Type.ARRAY) {
+			desc = type.getDescriptor();
+		} else { 
+			desc = type.getInternalName();
+		}
+		
+		mv.visitTypeInsn(opcode, desc);
+	}
+}

ProtocolLib/src/com/comphenix/protocol/reflect/compiler/CompileListener.java

@@ -0,0 +1,17 @@
+package com.comphenix.protocol.reflect.compiler;
+
+import com.comphenix.protocol.reflect.StructureModifier;
+
+/**
+ * Used to save the result of an compilation.
+ * 
+ * @author Kristian
+ * @param <TKey> - type of the structure modifier field.
+ */
+public interface CompileListener<TKey> {
+	/**
+	 * Invoked when a structure modifier has been successfully compiled.
+	 * @param compiledModifier - the compiled structure modifier.
+	 */
+	public void onCompiled(StructureModifier<TKey> compiledModifier);
+}

ProtocolLib/src/com/comphenix/protocol/reflect/compiler/CompiledStructureModifier.java

@@ -0,0 +1,73 @@
+package com.comphenix.protocol.reflect.compiler;
+
+import java.lang.reflect.Field;
+import java.util.Map;
+
+import com.comphenix.protocol.reflect.FieldAccessException;
+import com.comphenix.protocol.reflect.StructureModifier;
+import com.comphenix.protocol.reflect.instances.DefaultInstances;
+
+/**
+ * Represents a compiled structure modifier.
+ * 
+ * @author Kristian
+ * @param <TField> Field type.
+ */
+public abstract class CompiledStructureModifier<TField> extends StructureModifier<TField> {
+	// Used to compile instances of structure modifiers
+	protected StructureCompiler compiler;
+	
+	public CompiledStructureModifier() {
+		super();
+		customConvertHandling = true;
+	}
+	
+	// Speed up the default writer
+	@SuppressWarnings("unchecked")
+	@Override
+	public StructureModifier<TField> writeDefaults() throws FieldAccessException {
+		
+		DefaultInstances generator = DefaultInstances.DEFAULT;
+		
+		// Write a default instance to every field
+		for (Map.Entry<Field, Integer> entry  : defaultFields.entrySet()) {
+			Integer index = entry.getValue();
+			Field field = entry.getKey();
+			
+			write(index, (TField) generator.getDefault(field.getType()));
+		}
+		
+		return this;
+	}
+	
+	@SuppressWarnings("unchecked")
+	@Override
+	public final TField read(int fieldIndex) throws FieldAccessException {
+		Object result = readGenerated(fieldIndex);
+		
+		if (converter != null)
+			return converter.getSpecific(result);
+		else
+			return (TField) result;
+	}
+	
+	protected abstract Object readGenerated(int fieldIndex) throws FieldAccessException;
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public StructureModifier<TField> write(int index, Object value) throws FieldAccessException {
+		if (converter != null)
+			value = converter.getGeneric((TField) value);
+		return writeGenerated(index, value);
+	}
+	
+	protected abstract StructureModifier<TField> writeGenerated(int index, Object value) throws FieldAccessException;
+	
+	@Override
+	public StructureModifier<TField> withTarget(Object target) {
+		if (compiler != null)
+			return compiler.compile(super.withTarget(target));
+		else
+			return super.withTarget(target);
+	}
+}

ProtocolLib/src/com/comphenix/protocol/reflect/compiler/MethodDescriptor.java

@@ -0,0 +1,220 @@
+package com.comphenix.protocol.reflect.compiler;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import net.sf.cglib.asm.Type;
+
+/**
+ * Represents a method.
+ */
+class MethodDescriptor {
+
+    /**
+     * The method name.
+     */
+    private final String name;
+
+    /**
+     * The method descriptor.
+     */
+    private final String desc;
+
+    /**
+     * Maps primitive Java type names to their descriptors.
+     */
+    private static final Map<String, String> DESCRIPTORS;
+
+    static {
+        DESCRIPTORS = new HashMap<String, String>();
+        DESCRIPTORS.put("void", "V");
+        DESCRIPTORS.put("byte", "B");
+        DESCRIPTORS.put("char", "C");
+        DESCRIPTORS.put("double", "D");
+        DESCRIPTORS.put("float", "F");
+        DESCRIPTORS.put("int", "I");
+        DESCRIPTORS.put("long", "J");
+        DESCRIPTORS.put("short", "S");
+        DESCRIPTORS.put("boolean", "Z");
+    }
+
+    /**
+     * Creates a new {@link Method}.
+     * 
+     * @param name the method's name.
+     * @param desc the method's descriptor.
+     */
+    public MethodDescriptor(final String name, final String desc) {
+        this.name = name;
+        this.desc = desc;
+    }
+
+    /**
+     * Creates a new {@link Method}.
+     * 
+     * @param name the method's name.
+     * @param returnType the method's return type.
+     * @param argumentTypes the method's argument types.
+     */
+    public MethodDescriptor(
+        final String name,
+        final Type returnType,
+        final Type[] argumentTypes)
+    {
+        this(name, Type.getMethodDescriptor(returnType, argumentTypes));
+    }
+
+    /**
+     * Returns a {@link Method} corresponding to the given Java method
+     * declaration.
+     * 
+     * @param method a Java method declaration, without argument names, of the
+     *        form "returnType name (argumentType1, ... argumentTypeN)", where
+     *        the types are in plain Java (e.g. "int", "float",
+     *        "java.util.List", ...). Classes of the java.lang package can be
+     *        specified by their unqualified name; all other classes names must
+     *        be fully qualified.
+     * @return a {@link Method} corresponding to the given Java method
+     *         declaration.
+     * @throws IllegalArgumentException if <code>method</code> could not get
+     *         parsed.
+     */
+    public static MethodDescriptor getMethod(final String method)
+            throws IllegalArgumentException
+    {
+        return getMethod(method, false);
+    }
+
+    /**
+     * Returns a {@link Method} corresponding to the given Java method
+     * declaration.
+     * 
+     * @param method a Java method declaration, without argument names, of the
+     *        form "returnType name (argumentType1, ... argumentTypeN)", where
+     *        the types are in plain Java (e.g. "int", "float",
+     *        "java.util.List", ...). Classes of the java.lang package may be
+     *        specified by their unqualified name, depending on the
+     *        defaultPackage argument; all other classes names must be fully
+     *        qualified.
+     * @param defaultPackage true if unqualified class names belong to the
+     *        default package, or false if they correspond to java.lang classes.
+     *        For instance "Object" means "Object" if this option is true, or
+     *        "java.lang.Object" otherwise.
+     * @return a {@link Method} corresponding to the given Java method
+     *         declaration.
+     * @throws IllegalArgumentException if <code>method</code> could not get
+     *         parsed.
+     */
+    public static MethodDescriptor getMethod(
+        final String method,
+        final boolean defaultPackage) throws IllegalArgumentException
+    {
+        int space = method.indexOf(' ');
+        int start = method.indexOf('(', space) + 1;
+        int end = method.indexOf(')', start);
+        if (space == -1 || start == -1 || end == -1) {
+            throw new IllegalArgumentException();
+        }
+        String returnType = method.substring(0, space);
+        String methodName = method.substring(space + 1, start - 1).trim();
+        StringBuffer sb = new StringBuffer();
+        sb.append('(');
+        int p;
+        do {
+            String s;
+            p = method.indexOf(',', start);
+            if (p == -1) {
+                s = map(method.substring(start, end).trim(), defaultPackage);
+            } else {
+                s = map(method.substring(start, p).trim(), defaultPackage);
+                start = p + 1;
+            }
+            sb.append(s);
+        } while (p != -1);
+        sb.append(')');
+        sb.append(map(returnType, defaultPackage));
+        return new MethodDescriptor(methodName, sb.toString());
+    }
+
+    private static String map(final String type, final boolean defaultPackage) {
+        if ("".equals(type)) {
+            return type;
+        }
+
+        StringBuffer sb = new StringBuffer();
+        int index = 0;
+        while ((index = type.indexOf("[]", index) + 1) > 0) {
+            sb.append('[');
+        }
+
+        String t = type.substring(0, type.length() - sb.length() * 2);
+        String desc = (String) DESCRIPTORS.get(t);
+        if (desc != null) {
+            sb.append(desc);
+        } else {
+            sb.append('L');
+            if (t.indexOf('.') < 0) {
+                if (!defaultPackage) {
+                    sb.append("java/lang/");
+                }
+                sb.append(t);
+            } else {
+                sb.append(t.replace('.', '/'));
+            }
+            sb.append(';');
+        }
+        return sb.toString();
+    }
+
+    /**
+     * Returns the name of the method described by this object.
+     * 
+     * @return the name of the method described by this object.
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * Returns the descriptor of the method described by this object.
+     * 
+     * @return the descriptor of the method described by this object.
+     */
+    public String getDescriptor() {
+        return desc;
+    }
+
+    /**
+     * Returns the return type of the method described by this object.
+     * 
+     * @return the return type of the method described by this object.
+     */
+    public Type getReturnType() {
+        return Type.getReturnType(desc);
+    }
+
+    /**
+     * Returns the argument types of the method described by this object.
+     * 
+     * @return the argument types of the method described by this object.
+     */
+    public Type[] getArgumentTypes() {
+        return Type.getArgumentTypes(desc);
+    }
+
+    public String toString() {
+        return name + desc;
+    }
+
+    public boolean equals(final Object o) {
+        if (!(o instanceof MethodDescriptor)) {
+            return false;
+        }
+        MethodDescriptor other = (MethodDescriptor) o;
+        return name.equals(other.name) && desc.equals(other.desc);
+    }
+
+    public int hashCode() {
+        return name.hashCode() ^ desc.hashCode();
+    }
+}

ProtocolLib/src/com/comphenix/protocol/reflect/compiler/StructureCompiler.java

@@ -0,0 +1,443 @@
+package com.comphenix.protocol.reflect.compiler;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.comphenix.protocol.reflect.PrimitiveUtils;
+import com.comphenix.protocol.reflect.StructureModifier;
+import com.google.common.base.Objects;
+
+import net.sf.cglib.asm.*;
+
+// public class CompiledStructureModifierPacket20<TField> extends CompiledStructureModifier<TField> {
+//	
+//		private Packet20NamedEntitySpawn typedTarget;
+//	
+//		public CompiledStructureModifierPacket20(StructureModifier<TField> other, StructureCompiler compiler) {
+//			super();
+//			initialize(other);
+//			this.target = other.getTarget();
+//			this.typedTarget = (Packet20NamedEntitySpawn) target;
+//			this.compiler = compiler;
+//		}
+//	
+//		@Override
+//		protected Object readGenerated(int fieldIndex) throws FieldAccessException {
+//	
+//			Packet20NamedEntitySpawn target = typedTarget;
+//			
+//			switch (fieldIndex) {
+//			case 0: return (Object) target.a;
+//			case 1: return (Object) target.b;
+//			case 2: return (Object) target.c;
+//			case 3: return super.read(fieldIndex);
+//			case 4: return super.read(fieldIndex);
+//			case 5: return (Object) target.f;
+//			case 6: return (Object) target.g;
+//			case 7: return (Object) target.h;
+//			default:
+//				throw new FieldAccessException("Invalid index " + fieldIndex);
+//			}
+//		}
+//	
+//		@Override
+//		protected StructureModifier<TField> writeGenerated(int index, Object value) throws FieldAccessException {
+//			
+//			Packet20NamedEntitySpawn target = typedTarget;
+//			
+//			switch (index) {
+//			case 0: target.a = (Integer) value; break;
+//			case 1: target.b = (String) value; break;
+//			case 2: target.c = (Integer) value; break;
+//			case 3: target.d = (Integer) value; break;
+//			case 4: super.write(index, value); break;
+//			case 5: super.write(index, value); break;
+//			case 6: target.g = (Byte) value; break;
+//			case 7: target.h = (Integer) value; break;
+//			default:
+//				throw new FieldAccessException("Invalid index " + index);
+//			}
+//			
+//			// Chaining
+//			return this;
+//		}
+//	}
+
+/**
+ * Represents a StructureModifier compiler.
+ * 
+ * @author Kristian
+ */
+public final class StructureCompiler {
+
+	// Used to store generated classes of different types
+	@SuppressWarnings("rawtypes")
+	private class StructureKey {
+		private Class targetType;
+		private Class fieldType;
+		
+		public StructureKey(Class targetType, Class fieldType) {
+			this.targetType = targetType;
+			this.fieldType = fieldType;
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hashCode(targetType, fieldType);
+		}
+		
+		@Override
+		public boolean equals(Object obj) {
+			if (obj instanceof StructureKey) {
+				StructureKey other = (StructureKey) obj;
+				return Objects.equal(targetType, other.targetType) &&
+					   Objects.equal(fieldType, other.fieldType);
+			}
+			return false;
+		}
+	}
+	
+	// Used to load classes
+	private volatile static Method defineMethod;
+	
+	@SuppressWarnings("rawtypes")
+	private Map<StructureKey, Class> compiledCache = new HashMap<StructureKey, Class>();
+	
+	// The class loader we'll store our classes
+	private ClassLoader loader;
+	
+	// References to other classes
+	private static String PACKAGE_NAME = "com/comphenix/protocol/reflect/compiler";
+	private static String SUPER_CLASS = "com/comphenix/protocol/reflect/StructureModifier";
+	private static String COMPILED_CLASS = PACKAGE_NAME + "/CompiledStructureModifier";
+	private static String FIELD_EXCEPTION_CLASS = "com/comphenix/protocol/reflect/FieldAccessException";
+	
+	/**
+	 * Construct a structure compiler.
+	 * @param loader - main class loader.
+	 */
+	StructureCompiler(ClassLoader loader) {
+		this.loader = loader;
+	}
+	
+	/**
+	 * Compiles the given structure modifier.
+	 * <p>
+	 * WARNING: Do NOT call this method in the main thread. Compiling may easily take 10 ms, which is already 
+	 * over 1/4 of a tick (50 ms). Let the background thread automatically compile the structure modifiers instead.
+	 * @param source - structure modifier to compile.
+	 * @return A compiled structure modifier.
+	 */
+	@SuppressWarnings("unchecked")
+	public synchronized <TField> StructureModifier<TField> compile(StructureModifier<TField> source) {
+
+		// We cannot optimize a structure modifier with no public fields
+		if (!isAnyPublic(source.getFields())) {
+			return source;
+		}
+		
+		StructureKey key = new StructureKey(source.getTargetType(), source.getFieldType());
+		Class<?> compiledClass = compiledCache.get(key);
+		
+		if (!compiledCache.containsKey(key)) {
+			compiledClass = generateClass(source);
+			compiledCache.put(key, compiledClass);
+		}
+		
+		// Next, create an instance of this class
+		try {
+			return (StructureModifier<TField>) compiledClass.getConstructor(
+					StructureModifier.class, StructureCompiler.class).
+					 newInstance(source, this);
+		} catch (IllegalArgumentException e) {
+			throw new IllegalStateException("Used invalid parameters in instance creation", e);
+		} catch (SecurityException e) {
+			throw new RuntimeException("Security limitation!", e);
+		} catch (InstantiationException e) {
+			throw new RuntimeException("Error occured while instancing generated class.", e);
+		} catch (IllegalAccessException e) {
+			throw new RuntimeException("Security limitation! Cannot create instance of dynamic class.", e);
+		} catch (InvocationTargetException e) {
+			throw new RuntimeException("Error occured while instancing generated class.", e);
+		} catch (NoSuchMethodException e) {
+			throw new IllegalStateException("Cannot happen.", e);
+		}
+	}
+	
+	private <TField> Class<?> generateClass(StructureModifier<TField> source) {
+		
+		ClassWriter cw = new ClassWriter(0);
+
+		@SuppressWarnings("rawtypes")
+		Class targetType = source.getTargetType();
+		
+		String className = "CompiledStructure$" + targetType.getSimpleName() + source.getFieldType().getSimpleName();
+		String targetSignature = Type.getDescriptor(targetType);
+		String targetName = targetType.getName().replace('.', '/');
+		
+		try {
+			// This class might have been generated before. Try to load it.
+			Class<?> before = loader.loadClass(PACKAGE_NAME.replace('/', '.') + "." + className);
+			
+			if (before != null)
+				return before;
+		} catch (ClassNotFoundException e) {
+			// That's ok. 
+		}
+		
+		cw.visit(Opcodes.V1_6, Opcodes.ACC_PUBLIC + Opcodes.ACC_SUPER, PACKAGE_NAME + "/" + className, 
+				"<TField:Ljava/lang/Object;>L" + COMPILED_CLASS + "<TTField;>;", 
+				COMPILED_CLASS, null);
+
+		createFields(cw, targetSignature);
+		createConstructor(cw, className, targetSignature, targetName);
+		createReadMethod(cw, className, source.getFields(), targetSignature, targetName);
+		createWriteMethod(cw, className, source.getFields(), targetSignature, targetName);
+		cw.visitEnd();
+
+		byte[] data = cw.toByteArray();
+		
+		// Call the define method
+		try {
+			if (defineMethod == null) {
+				Method defined = ClassLoader.class.getDeclaredMethod("defineClass", 
+					new Class<?>[] { String.class, byte[].class, int.class, int.class });
+			
+				// Awesome. Now, create and return it.
+				defined.setAccessible(true);
+				defineMethod = defined;
+			}
+			
+			@SuppressWarnings("rawtypes")
+			Class clazz = (Class) defineMethod.invoke(loader, null, data, 0, data.length);
+			
+			// DEBUG CODE: Print the content of the generated class.
+			//org.objectweb.asm.ClassReader cr = new org.objectweb.asm.ClassReader(data);
+	        //cr.accept(new ASMifierClassVisitor(new PrintWriter(System.out)), 0);
+			
+			return clazz;
+			
+		} catch (SecurityException e) {
+			throw new RuntimeException("Cannot use reflection to dynamically load a class.", e);
+		} catch (NoSuchMethodException e) {
+			throw new IllegalStateException("Incompatible JVM.", e);
+		} catch (IllegalArgumentException e) {
+			throw new IllegalStateException("Cannot call defineMethod - wrong JVM?", e);
+		} catch (IllegalAccessException e) {
+			throw new RuntimeException("Security limitation! Cannot dynamically load class.", e);
+		} catch (InvocationTargetException e) {
+			throw new RuntimeException("Error occured in code generator.", e);
+		}
+	}
+	
+	/**
+	 * Determine if at least one of the given fields is public.
+	 * @param fields - field to test.
+	 * @return TRUE if one or more field is publically accessible, FALSE otherwise.
+	 */
+	private boolean isAnyPublic(List<Field> fields) {
+		// Are any of the fields public?
+		for (int i = 0; i < fields.size(); i++) {
+			if (isPublic(fields.get(i))) {
+				return true;
+			}
+		}
+		
+		return false;
+	}
+	
+	private boolean isPublic(Field field) {
+		return Modifier.isPublic(field.getModifiers());
+	}
+	
+	private void createFields(ClassWriter cw, String targetSignature) {
+		FieldVisitor typedField = cw.visitField(Opcodes.ACC_PRIVATE, "typedTarget", targetSignature, null, null);
+		typedField.visitEnd();
+	}
+	
+	private void createWriteMethod(ClassWriter cw, String className, List<Field> fields, String targetSignature, String targetName) {
+		
+		String methodDescriptor = "(ILjava/lang/Object;)L" + SUPER_CLASS + ";";
+		String methodSignature = "(ITTField;)L" + SUPER_CLASS + "<TTField;>;";
+		MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PROTECTED, "writeGenerated", methodDescriptor, methodSignature, 
+									new String[] { FIELD_EXCEPTION_CLASS });
+		BoxingHelper boxingHelper = new BoxingHelper(mv);
+		
+		mv.visitCode();
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitFieldInsn(Opcodes.GETFIELD, PACKAGE_NAME + "/" + className, "typedTarget", targetSignature);
+		mv.visitVarInsn(Opcodes.ASTORE, 3);
+		mv.visitVarInsn(Opcodes.ILOAD, 1);
+
+		// The last label is for the default switch
+		Label[] labels = new Label[fields.size()];
+		Label errorLabel = new Label();
+		Label returnLabel = new Label();
+		
+		// Generate labels
+		for (int i = 0; i < fields.size(); i++) {
+			labels[i] = new Label();
+		}
+		
+		mv.visitTableSwitchInsn(0, labels.length - 1, errorLabel, labels);
+		
+		for (int i = 0; i < fields.size(); i++) {
+			
+			Class<?> outputType = fields.get(i).getType();
+			Class<?> inputType = PrimitiveUtils.wrap(outputType);
+			String typeDescriptor = Type.getDescriptor(outputType);
+			String inputPath = inputType.getName().replace('.', '/');
+			
+			mv.visitLabel(labels[i]);
+			
+			// Push the compare object
+			if (i == 0)
+				mv.visitFrame(Opcodes.F_APPEND, 1, new Object[] { targetName }, 0, null);
+			else
+				mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
+			
+			// Only write to public fields
+			if (isPublic(fields.get(i))) {
+				mv.visitVarInsn(Opcodes.ALOAD, 3);
+				mv.visitVarInsn(Opcodes.ALOAD, 2);
+				
+				if (!PrimitiveUtils.isPrimitive(outputType))
+					mv.visitTypeInsn(Opcodes.CHECKCAST, inputPath);
+				else
+					boxingHelper.unbox(Type.getType(outputType));
+				
+				mv.visitFieldInsn(Opcodes.PUTFIELD, targetName, fields.get(i).getName(), typeDescriptor);
+			
+			} else {
+				// Use reflection. We don't have a choice, unfortunately.
+				mv.visitVarInsn(Opcodes.ALOAD, 0);
+				mv.visitVarInsn(Opcodes.ILOAD, 1);
+				mv.visitVarInsn(Opcodes.ALOAD, 2);
+				mv.visitMethodInsn(Opcodes.INVOKESPECIAL, COMPILED_CLASS, "write", "(ILjava/lang/Object;)L" + SUPER_CLASS + ";");
+				mv.visitInsn(Opcodes.POP);
+			}
+		
+			mv.visitJumpInsn(Opcodes.GOTO, returnLabel);
+		}
+		
+		mv.visitLabel(errorLabel);
+		mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
+		mv.visitTypeInsn(Opcodes.NEW, FIELD_EXCEPTION_CLASS);
+		mv.visitInsn(Opcodes.DUP);
+		mv.visitTypeInsn(Opcodes.NEW, "java/lang/StringBuilder");
+		mv.visitInsn(Opcodes.DUP);
+		mv.visitLdcInsn("Invalid index ");
+		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V");
+		mv.visitVarInsn(Opcodes.ILOAD, 1);
+		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;");
+		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
+		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, FIELD_EXCEPTION_CLASS, "<init>", "(Ljava/lang/String;)V");
+		mv.visitInsn(Opcodes.ATHROW);
+		
+		mv.visitLabel(returnLabel);
+		mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitInsn(Opcodes.ARETURN);
+		mv.visitMaxs(5, 4);
+		mv.visitEnd();
+	}
+
+	private void createReadMethod(ClassWriter cw, String className, List<Field> fields, String targetSignature, String targetName) {
+		MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PROTECTED, "readGenerated", "(I)Ljava/lang/Object;", null, 
+									new String[] { "com/comphenix/protocol/reflect/FieldAccessException" });
+		BoxingHelper boxingHelper = new BoxingHelper(mv);
+		
+		mv.visitCode();
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitFieldInsn(Opcodes.GETFIELD, PACKAGE_NAME + "/" + className, "typedTarget", targetSignature);
+		mv.visitVarInsn(Opcodes.ASTORE, 2);
+		mv.visitVarInsn(Opcodes.ILOAD, 1);
+
+		// The last label is for the default switch
+		Label[] labels = new Label[fields.size()];
+		Label errorLabel = new Label();
+		
+		// Generate labels
+		for (int i = 0; i < fields.size(); i++) {
+			labels[i] = new Label();
+		}
+		
+		mv.visitTableSwitchInsn(0, fields.size() - 1, errorLabel, labels);
+		
+		for (int i = 0; i < fields.size(); i++) {
+			Class<?> outputType = fields.get(i).getType();
+			String typeDescriptor = Type.getDescriptor(outputType);
+			
+			mv.visitLabel(labels[i]);
+			
+			// Push the compare object
+			if (i == 0)
+				mv.visitFrame(Opcodes.F_APPEND, 1, new Object[] { targetName }, 0, null);
+			else
+				mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
+			
+			// Note that byte code cannot access non-public fields
+			if (isPublic(fields.get(i))) {
+				mv.visitVarInsn(Opcodes.ALOAD, 2);
+				mv.visitFieldInsn(Opcodes.GETFIELD, targetName, fields.get(i).getName(), typeDescriptor);
+				
+				boxingHelper.box(Type.getType(outputType));
+			} else {
+				// We have to use reflection for private and protected fields.
+				mv.visitVarInsn(Opcodes.ALOAD, 0);
+				mv.visitVarInsn(Opcodes.ILOAD, 1);
+				mv.visitMethodInsn(Opcodes.INVOKESPECIAL, COMPILED_CLASS, "read", "(I)Ljava/lang/Object;");
+			}
+			
+			mv.visitInsn(Opcodes.ARETURN);
+		}
+
+		mv.visitLabel(errorLabel);
+		mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
+		mv.visitTypeInsn(Opcodes.NEW, FIELD_EXCEPTION_CLASS);
+		mv.visitInsn(Opcodes.DUP);
+		mv.visitTypeInsn(Opcodes.NEW, "java/lang/StringBuilder");
+		mv.visitInsn(Opcodes.DUP);
+		mv.visitLdcInsn("Invalid index ");
+		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V");
+		mv.visitVarInsn(Opcodes.ILOAD, 1);
+		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;");
+		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;");
+		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, FIELD_EXCEPTION_CLASS, "<init>", "(Ljava/lang/String;)V");
+		mv.visitInsn(Opcodes.ATHROW);
+		mv.visitMaxs(5, 3);
+		mv.visitEnd();
+	}
+
+	private void createConstructor(ClassWriter cw, String className, String targetSignature, String targetName) {
+		MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", 
+				"(L" + SUPER_CLASS + ";L" + PACKAGE_NAME + "/StructureCompiler;)V", 
+				"(L" + SUPER_CLASS + "<TTField;>;L" + SUPER_CLASS + ";)V", null);
+		mv.visitCode();
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitMethodInsn(Opcodes.INVOKESPECIAL, COMPILED_CLASS, "<init>", "()V");
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitVarInsn(Opcodes.ALOAD, 1);
+		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, PACKAGE_NAME + "/" + className, "initialize", "(L" + SUPER_CLASS + ";)V");
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitVarInsn(Opcodes.ALOAD, 1);
+		mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, SUPER_CLASS, "getTarget", "()Ljava/lang/Object;");
+		mv.visitFieldInsn(Opcodes.PUTFIELD, PACKAGE_NAME + "/" + className, "target", "Ljava/lang/Object;");
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitFieldInsn(Opcodes.GETFIELD, PACKAGE_NAME + "/" + className, "target", "Ljava/lang/Object;");
+		mv.visitTypeInsn(Opcodes.CHECKCAST, targetName);
+		mv.visitFieldInsn(Opcodes.PUTFIELD, PACKAGE_NAME + "/" + className, "typedTarget", targetSignature);
+		mv.visitVarInsn(Opcodes.ALOAD, 0);
+		mv.visitVarInsn(Opcodes.ALOAD, 2);
+		mv.visitFieldInsn(Opcodes.PUTFIELD, PACKAGE_NAME + "/" + className, "compiler", "L" + PACKAGE_NAME + "/StructureCompiler;");
+		mv.visitInsn(Opcodes.RETURN);
+		mv.visitMaxs(2, 3);
+		mv.visitEnd();
+	}
+}

ProtocolLib/src/com/comphenix/protocol/reflect/instances/DefaultInstances.java

@@ -20,6 +20,8 @@ package com.comphenix.protocol.reflect.instances;
 import java.lang.reflect.Constructor;
 import java.util.*;
 
+import net.sf.cglib.proxy.Enhancer;
+
 import com.google.common.base.Objects;
 import com.google.common.collect.ImmutableList;
 
@@ -100,6 +102,38 @@ public class DefaultInstances {
 		return getDefaultInternal(type, registered, 0);
 	}
 	
+	/**
+	 * Retrieve the constructor with the fewest number of parameters.
+	 * @param type - type to construct.
+	 * @return A constructor with the fewest number of parameters, or NULL if the type has no constructors.
+	 */
+	@SuppressWarnings("unchecked")
+	public <T> Constructor<T> getMinimumConstructor(Class<T> type) {
+		
+		Constructor<T> minimum = null;
+		int lastCount = Integer.MAX_VALUE;
+		
+		// Find the constructor with the fewest parameters
+		for (Constructor<?> candidate : type.getConstructors()) {
+			Class<?>[] types = candidate.getParameterTypes();
+			
+			// Note that we don't allow recursive types - that is, types that
+			// require itself in the constructor.
+			if (types.length < lastCount) {
+				if (!contains(types, type)) {
+					minimum = (Constructor<T>) candidate;
+					lastCount = types.length;
+					
+					// Don't loop again if we've already found the best possible constructor
+					if (lastCount == 0)
+						break;
+				}
+			}
+		}
+		
+		return minimum;
+	}
+	
 	/**
 	 * Retrieves a default instance or value that is assignable to this type.
 	 * <p>
@@ -136,36 +170,18 @@ public class DefaultInstances {
 			if (value != null)
 				return (T) value;
 		}
-		
-		Constructor<T> minimum = null;
-		int lastCount = Integer.MAX_VALUE;
-		
-		// Find the constructor with the fewest parameters
-		for (Constructor<?> candidate : type.getConstructors()) {
-			Class<?>[] types = candidate.getParameterTypes();
-			
-			// Note that we don't allow recursive types - that is, types that
-			// require itself in the constructor.
-			if (types.length < lastCount) {
-				if (!contains(types, type)) {
-					minimum = (Constructor<T>) candidate;
-					lastCount = types.length;
-					
-					// Don't loop again if we've already found the best possible constructor
-					if (lastCount == 0)
-						break;
-				}
-			}
-		}
-		
+
+		Constructor<T> minimum = getMinimumConstructor(type);
+
 		// Create the type with this constructor using default values. This might fail, though.
 		try {
 			if (minimum != null) {
-				Object[] params = new Object[lastCount];
+				int parameterCount = minimum.getParameterTypes().length;
+				Object[] params = new Object[parameterCount];
 				Class<?>[] types = minimum.getParameterTypes();
 				
 				// Fill out 
-				for (int i = 0; i < lastCount; i++) {
+				for (int i = 0; i < parameterCount; i++) {
 					params[i] = getDefaultInternal(types[i], providers, recursionLevel + 1);
 				}
 				
@@ -180,6 +196,24 @@ public class DefaultInstances {
 		return null;
 	}
 	
+	/**
+	 * Construct default instances using the CGLIB enhancer object instead.
+	 * @param enhancer - a CGLIB enhancer to use.
+	 * @return A default instance generator that uses the CGLIB enhancer.
+	 */
+	public DefaultInstances forEnhancer(Enhancer enhancer) {
+		final Enhancer ex = enhancer;
+		
+		return new DefaultInstances(registered) {
+			@SuppressWarnings("unchecked")
+			@Override
+			protected <T> T createInstance(Class<T> type, Constructor<T> constructor, Class<?>[] types, Object[] params) {
+				// Use the enhancer instead
+				return (T) ex.create(types, params);
+			}
+		};
+	}
+	
 	/**
 	 * Used by the default instance provider to create a class from a given constructor. 
 	 * The default method uses reflection.

ProtocolLib/src/com/comphenix/protocol/reflect/instances/ExistingGenerator.java

@@ -0,0 +1,89 @@
+package com.comphenix.protocol.reflect.instances;
+
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.Map;
+
+import javax.annotation.Nullable;
+
+import com.comphenix.protocol.reflect.FieldUtils;
+import com.comphenix.protocol.reflect.FuzzyReflection;
+
+/**
+ * Provides instance constructors using a list of existing values.
+ * <p>
+ * Only one instance per individual class.
+ * @author Kristian
+ */
+public class ExistingGenerator implements InstanceProvider {
+
+	@SuppressWarnings("rawtypes")
+	private Map<Class, Object> existingValues = new HashMap<Class, Object>();
+	
+	private ExistingGenerator() {
+		// Only accessible to the constructors
+	}
+	
+	/**
+	 * Automatically create an instance provider from a objects public and private fields.
+	 * <p>
+	 * If two or more fields share the same type, the last declared non-null field will take
+	 * precedent.
+	 * @param object - object to create an instance generator from.
+	 * @return The instance generator.
+	 */
+	public static ExistingGenerator fromObjectFields(Object object) {
+		ExistingGenerator generator = new ExistingGenerator();
+		
+		// Read instances from every field.
+		for (Field field : FuzzyReflection.fromObject(object, true).getFields()) {
+			try {
+				Object value = FieldUtils.readField(field, object, true);
+				
+				// Use the type of the field, not the object itself
+				if (value != null)
+					generator.addObject(field.getType(), value);
+				
+			} catch (Exception e) {
+				// Yes, swallow it. No, really.
+			}
+		}
+		
+		return generator;
+	}
+	
+	/**
+	 * Create an instance generator from a pre-defined array of values.
+	 * @param values - values to provide.
+	 * @return An instance provider that uses these values.
+	 */
+	public static ExistingGenerator fromObjectArray(Object[] values) {
+		ExistingGenerator generator = new ExistingGenerator();
+		
+		for (Object value : values)
+			 generator.addObject(value);
+		
+		return generator;
+	}
+	
+	private void addObject(Object value) {
+		if (value == null)
+			throw new IllegalArgumentException("Value cannot be NULL.");
+		
+		existingValues.put(value.getClass(), value);
+	}
+
+	private void addObject(Class<?> type, Object value) {
+		existingValues.put(type, value);
+	}
+
+	
+	@Override
+	public Object create(@Nullable Class<?> type) {
+		
+		Object value = existingValues.get(type);
+		
+		// NULL values indicate that the generator failed
+		return value;
+	}
+}

ProtocolLib/src/plugin.yml

@@ -1,5 +1,5 @@
 name: ProtocolLib
-version: 1.1.0
+version: 1.2.0
 description: Provides read/write access to the Minecraft protocol.
 author: Comphenix
 website: http://www.comphenix.net/ProtocolLib

Readme.md

@@ -129,5 +129,3 @@ types. It's remarkably consistent across different versions.
 ### Incompatiblity
 
 The following plugins (to be expanded) are not compatible with ProtocolLib:
-
- * TagAPI