Ensure that the structure compiler is thread safe.

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/compiler/BackgroundCompiler.java

@@ -80,6 +80,27 @@ public class BackgroundCompiler {
 	@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) {
 			
@@ -92,11 +113,11 @@ public class BackgroundCompiler {
 					@Override
 					public Object call() throws Exception {
 		
-						StructureModifier<?> modifier = cache.get(key);
+						StructureModifier<TKey> modifier = uncompiled;
 						
-						// Update the cache!
+						// Do our compilation
 						modifier = compiler.compile(modifier);
-						cache.put(key, modifier);
+						listener.onCompiled(modifier);
 						
 						// We'll also return the new structure modifier
 						return modifier;

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);
+}