Experimental fix for issue #7 on Github.

Attempt to detect the correct "get" method in a IntHashMap.

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

@@ -21,7 +21,6 @@ import java.lang.reflect.Constructor;
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
-import java.lang.reflect.Modifier;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
@@ -35,8 +34,8 @@ import org.bukkit.entity.Player;
 import com.comphenix.protocol.reflect.FieldAccessException;
 import com.comphenix.protocol.reflect.FieldUtils;
 import com.comphenix.protocol.reflect.FuzzyReflection;
-import com.comphenix.protocol.reflect.fuzzy.FuzzyMethodContract;
 import com.comphenix.protocol.utility.MinecraftReflection;
+import com.comphenix.protocol.wrappers.WrappedIntHashMap;
 import com.google.common.collect.Lists;
 
 /**
@@ -51,7 +50,6 @@ class EntityUtilities {
 	private static Field trackedPlayersField;
 	private static Field trackerField;
 	
-	private static Method hashGetMethod;
 	private static Method scanPlayersMethod;
 
 	/*
@@ -204,35 +202,7 @@ class EntityUtilities {
 			throw new FieldAccessException("Cannot access 'trackedEntities' field due to security limitations.", e);
 		}
 		
-		// Getting the "get" method is pretty hard, but first - try to just get it by name
-		if (hashGetMethod == null) {
-			
-			Class<?> type = trackedEntities.getClass();
-			
-			try {
-				hashGetMethod = type.getMethod("get", int.class);
-			} catch (NoSuchMethodException e) {
-				// Then it's probably the lowest named method that takes an int-parameter and returns a object
-				hashGetMethod = FuzzyReflection.fromClass(type).getMethod(
-					FuzzyMethodContract.newBuilder().banModifier(Modifier.STATIC).
-					parameterCount(1).
-					parameterExactType(int.class).
-					returnTypeExact(Object.class).
-					build()
-				);
-			}
-		}
-		
-		// Wrap exceptions
-		try {
-			return hashGetMethod.invoke(trackedEntities, entityID);
-		} catch (IllegalArgumentException e) {
-			throw e;
-		} catch (IllegalAccessException e) {
-			throw new FieldAccessException("Security limitation prevents access to 'get' method in IntHashMap", e);
-		} catch (InvocationTargetException e) {
-			throw new RuntimeException("Exception occurred in Minecraft.", e);
-		}
+		return WrappedIntHashMap.fromHandle(trackedEntities).get(entityID);
 	}
 	
 	/**

ProtocolLib/src/main/java/com/comphenix/protocol/injector/packet/ProxyPacketInjector.java

@@ -20,7 +20,6 @@ package com.comphenix.protocol.injector.packet;
 import java.io.DataInput;
 import java.io.DataInputStream;
 import java.lang.reflect.Field;
-import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Map;
 import java.util.Set;
@@ -48,6 +47,7 @@ import com.comphenix.protocol.reflect.FuzzyReflection;
 import com.comphenix.protocol.reflect.MethodInfo;
 import com.comphenix.protocol.reflect.fuzzy.FuzzyMethodContract;
 import com.comphenix.protocol.utility.MinecraftReflection;
+import com.comphenix.protocol.wrappers.WrappedIntHashMap;
 
 /**
  * This class is responsible for adding or removing proxy objects that intercepts recieved packets.
@@ -67,9 +67,7 @@ class ProxyPacketInjector implements PacketInjector {
 	}
 	
 	private static class IntHashMapLookup implements PacketClassLookup {
-		// The "put" method that associates a packet ID with a packet class
-		private Method putMethod;
-		private Object intHashMap;
+		private WrappedIntHashMap intHashMap;
 		
 		public IntHashMapLookup() throws IllegalAccessException {
 			initialize();
@@ -77,32 +75,21 @@ class ProxyPacketInjector implements PacketInjector {
 		
 		@Override
 		public void setLookup(int packetID, Class<?> clazz) {
-			try {
-				putMethod.invoke(intHashMap, packetID, clazz);
-			} catch (IllegalArgumentException e) {
-				throw new RuntimeException("Illegal argument.", e);
-			} catch (IllegalAccessException e) {
-				throw new RuntimeException("Cannot access method.", e);
-			} catch (InvocationTargetException e) {
-				throw new RuntimeException("Exception occured in IntHashMap.put.", e);
-			}
+			intHashMap.put(packetID, clazz);
 		}
 
 		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.
 				Field intHashMapField = FuzzyReflection.fromClass(MinecraftReflection.getPacketClass(), true).
-						getFieldByType(MinecraftReflection.getMinecraftObjectRegex());
+						getFieldByType("packetIdMap", MinecraftReflection.getIntHashMapClass());
 				
 				try {
-					intHashMap = FieldUtils.readField(intHashMapField, (Object) null, true);
+					intHashMap = WrappedIntHashMap.fromHandle(
+						FieldUtils.readField(intHashMapField, (Object) null, true));
 				} catch (IllegalArgumentException e) {
 					throw new RuntimeException("Minecraft is incompatible.", e);
 				}
-				
-				// Now, get the "put" method.
-				putMethod = FuzzyReflection.fromObject(intHashMap).
-						getMethodByParameters("put", int.class, Object.class);
 			}
 		}
 	}

ProtocolLib/src/main/java/com/comphenix/protocol/reflect/fuzzy/AbstractFuzzyMember.java

@@ -1,6 +1,7 @@
 package com.comphenix.protocol.reflect.fuzzy;
 
 import java.lang.reflect.Member;
+import java.lang.reflect.Modifier;
 import java.util.Map;
 import java.util.regex.Pattern;
 
@@ -46,6 +47,14 @@ public abstract class AbstractFuzzyMember<T extends Member> extends AbstractFuzz
 			return this;
 		}
 		
+		/**
+		 * Require that every matching member is public.
+		 * @return This builder, for chaining.
+		 */
+		public Builder<T> requirePublic() {
+			return requireModifier(Modifier.PUBLIC);
+		}
+		
 		/**
 		 * Add a given bit-field of modifers that will skip or ignore members.
 		 * @param modifier - bit-field of modifiers to skip or ignore.

ProtocolLib/src/main/java/com/comphenix/protocol/reflect/fuzzy/FuzzyFieldContract.java

@@ -34,6 +34,12 @@ public class FuzzyFieldContract extends AbstractFuzzyMember<Field> {
 			return this;
 		}
 		
+		@Override
+		public Builder requirePublic() {
+			super.requirePublic();
+			return this;
+		}
+		
 		@Override
 		public Builder nameRegex(String regex) {
 			super.nameRegex(regex); 

ProtocolLib/src/main/java/com/comphenix/protocol/reflect/fuzzy/FuzzyMatchers.java

@@ -4,6 +4,9 @@ import java.lang.reflect.Member;
 import java.util.Set;
 import java.util.regex.Pattern;
 
+import javax.annotation.Nonnull;
+
+import com.google.common.base.Preconditions;
 import com.google.common.collect.Sets;
 
 /**
@@ -12,14 +15,56 @@ import com.google.common.collect.Sets;
  * @author Kristian
  */
 public class FuzzyMatchers {
+	// Constant matchers
+	private static AbstractFuzzyMatcher<Class<?>> MATCH_ALL = new AbstractFuzzyMatcher<Class<?>>() {
+		@Override
+		public boolean isMatch(Class<?> value, Object parent) {
+			return true;
+		}
+		
+		@Override
+		protected int calculateRoundNumber() {
+			return 0;
+		}
+	};
+	
 	private FuzzyMatchers() {
 		// Don't make this constructable
 	}
 
+	/**
+	 * Construct a class matcher that matches an array with a given component matcher.
+	 * @param componentMatcher - the component matcher.
+	 * @return A new array matcher.
+	 */
+	public static AbstractFuzzyMatcher<Class<?>> matchArray(@Nonnull final AbstractFuzzyMatcher<Class<?>> componentMatcher) {
+		Preconditions.checkNotNull(componentMatcher, "componentMatcher cannot be NULL.");
+		return new AbstractFuzzyMatcher<Class<?>>() {
+			@Override
+			public boolean isMatch(Class<?> value, Object parent) {
+				return value.isArray() && componentMatcher.isMatch(value.getComponentType(), parent);
+			}
+			
+			@Override
+			protected int calculateRoundNumber() {
+				// We're just above object
+				return -1;
+			}
+		};
+	}
+	
+	/**
+	 * Retrieve a fuzzy matcher that will match any class.
+	 * @return A class matcher.
+	 */
+	public static AbstractFuzzyMatcher<Class<?>> matchAll() {
+		return MATCH_ALL;
+	}
+	
 	/**
 	 * Construct a class matcher that matches types exactly.
 	 * @param matcher - the matching class.
-	 * @return A new class mathcher.
+	 * @return A new class matcher.
 	 */
 	public static AbstractFuzzyMatcher<Class<?>> matchExact(Class<?> matcher) {
 		return new ClassExactMatcher(matcher, ClassExactMatcher.Options.MATCH_EXACT);
@@ -28,7 +73,7 @@ public class FuzzyMatchers {
 	/**
 	 * Construct a class matcher that matches any of the given classes exactly.
 	 * @param classes - list of classes to match.
-	 * @return A new class mathcher.
+	 * @return A new class matcher.
 	 */
 	public static AbstractFuzzyMatcher<Class<?>> matchAnyOf(Class<?>... classes) {
 		return matchAnyOf(Sets.newHashSet(classes));
@@ -37,7 +82,7 @@ public class FuzzyMatchers {
 	/**
 	 * Construct a class matcher that matches any of the given classes exactly.
 	 * @param classes - set of classes to match.
-	 * @return A new class mathcher.
+	 * @return A new class matcher.
 	 */
 	public static AbstractFuzzyMatcher<Class<?>> matchAnyOf(Set<Class<?>> classes) {
 		return new ClassSetMatcher(classes);
@@ -46,7 +91,7 @@ public class FuzzyMatchers {
 	/**
 	 * Construct a class matcher that matches super types of the given class.
 	 * @param matcher - the matching type must be a super class of this type.
-	 * @return A new class mathcher.
+	 * @return A new class matcher.
 	 */
 	public static AbstractFuzzyMatcher<Class<?>> matchSuper(Class<?> matcher) {
 		return new ClassExactMatcher(matcher, ClassExactMatcher.Options.MATCH_SUPER);
@@ -55,7 +100,7 @@ public class FuzzyMatchers {
 	/**
 	 * Construct a class matcher that matches derived types of the given class.
 	 * @param matcher - the matching type must be a derived class of this type.
-	 * @return A new class mathcher.
+	 * @return A new class matcher.
 	 */
 	public static AbstractFuzzyMatcher<Class<?>> matchDerived(Class<?> matcher) {
 		return new ClassExactMatcher(matcher, ClassExactMatcher.Options.MATCH_DERIVED);

ProtocolLib/src/main/java/com/comphenix/protocol/reflect/fuzzy/FuzzyMethodContract.java

@@ -98,6 +98,12 @@ public class FuzzyMethodContract extends AbstractFuzzyMember<MethodInfo> {
 			return this;
 		}
 		
+		@Override
+		public Builder requirePublic() {
+			super.requirePublic();
+			return this;
+		}
+		
 		@Override
 		public Builder banModifier(int modifier) {
 			super.banModifier(modifier); 

ProtocolLib/src/main/java/com/comphenix/protocol/utility/MinecraftReflection.java

@@ -419,6 +419,15 @@ public class MinecraftReflection {
 		return getDataWatcherClass().isAssignableFrom(obj.getClass());
 	}
 	
+	/**
+	 * Determine if the given object is an IntHashMap object.
+	 * @param obj - the given object.
+	 * @return TRUE if it is, FALSE otherwise.
+	 */
+	public static boolean isIntHashMap(Object obj) {
+		return getIntHashMapClass().isAssignableFrom(obj.getClass());
+	}
+	
 	/**
 	 * Determine if the given object is a CraftItemStack instancey.
 	 * @param obj - the given object.
@@ -1010,6 +1019,45 @@ public class MinecraftReflection {
 		}
 	}
 	
+	/**
+	 * Retrieve the IntHashMap class.
+	 * @return IntHashMap class.
+	 */
+	public static Class<?> getIntHashMapClass() {
+		try {
+			return getMinecraftClass("IntHashMap");
+		} catch (RuntimeException e) {
+			final Class<?> parent = getEntityTrackerClass();
+
+			// Expected structure of a IntHashMap
+			final FuzzyClassContract intHashContract = FuzzyClassContract.newBuilder().
+				// add(int key, Object value)
+				method(FuzzyMethodContract.newBuilder().
+						parameterCount(2).
+						parameterExactType(int.class, 0).
+						parameterExactType(Object.class, 1).requirePublic()
+				).
+				// Object get(int key)
+				method(FuzzyMethodContract.newBuilder().
+						parameterCount(1).
+						parameterExactType(int.class).
+						returnTypeExact(Object.class).requirePublic()
+				).
+				// Finally, there should be an array of some kind
+				field(FuzzyFieldContract.newBuilder().
+						typeMatches(FuzzyMatchers.matchArray(FuzzyMatchers.matchAll()))
+				).
+			build();
+
+			final AbstractFuzzyMatcher<Field> intHashField = FuzzyFieldContract.newBuilder().
+				typeMatches(getMinecraftObjectMatcher().and(intHashContract)).
+				build();
+			
+			// Use the type of the first field that matches
+			return setMinecraftClass("IntHashMap", FuzzyReflection.fromClass(parent).getField(intHashField).getType());
+		}
+	}
+	
 	/**
 	 * Retrieve the attribute modifier class.
 	 * @return Attribute modifier class.
@@ -1295,6 +1343,4 @@ public class MinecraftReflection {
 	public static String getNetLoginHandlerName() {
 		return getNetLoginHandlerClass().getSimpleName();
 	}
-
-
 }

ProtocolLib/src/main/java/com/comphenix/protocol/wrappers/WrappedIntHashMap.java

@@ -0,0 +1,176 @@
+package com.comphenix.protocol.wrappers;
+
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import javax.annotation.Nonnull;
+
+import com.comphenix.protocol.reflect.FuzzyReflection;
+import com.comphenix.protocol.reflect.fuzzy.FuzzyMethodContract;
+import com.comphenix.protocol.utility.MinecraftReflection;
+import com.google.common.base.Preconditions;
+
+/**
+ * Represents a wrapper for the internal IntHashMap in Minecraft.
+ * @author Kristian
+ */
+public class WrappedIntHashMap {
+	private static final Class<?> INT_HASH_MAP = MinecraftReflection.getIntHashMapClass();
+	
+	private static Method PUT_METHOD;
+	private static Method GET_METHOD;
+	
+	private Object handle;
+	
+	/**
+	 * Construct an IntHashMap wrapper around an instance.
+	 * @param handle - the NMS instance.
+	 */
+	private WrappedIntHashMap(Object handle) {		
+		this.handle = handle;
+	}
+	
+	/**
+	 * Construct a new IntHashMap.
+	 * @return A new IntHashMap.
+	 */
+	public static WrappedIntHashMap newMap() {
+		try {
+			return new WrappedIntHashMap(INT_HASH_MAP.newInstance());
+		} catch (Exception e) {
+			throw new RuntimeException("Unable to construct IntHashMap.", e);
+		}
+	}
+	
+	/**
+	 * Construct a wrapper around a given NMS IntHashMap.
+	 * @param handle - the NMS IntHashMap.
+	 * @return The created wrapped.
+	 * @throws IllegalArgumentException If the handle is not an IntHasMap.
+	 */
+	public static WrappedIntHashMap fromHandle(@Nonnull Object handle) {
+		Preconditions.checkNotNull(handle, "handle cannot be NULL");
+		Preconditions.checkState(MinecraftReflection.isIntHashMap(handle), 
+				"handle is a " + handle.getClass() + ", not an IntHashMap.");
+
+		return new WrappedIntHashMap(handle);
+	}
+	
+	/**
+	 * Associates a specified key with the given value in the integer map. 
+	 * <p>
+	 * If the key has already been associated with a value, then it will be replaced by the new value.
+	 * @param key - the key to insert.
+	 * @param value - the value to insert. Cannot be NULL.
+	 * @throws RuntimeException If the reflection machinery failed.
+	 */
+	public void put(int key, Object value) {
+		Preconditions.checkNotNull(value, "value cannot be NULL.");
+		
+		initializePutMethod();
+		putInternal(key, value);
+	}
+	
+	/**
+	 * Invoked when a value must be inserted into the underlying map, regardless of preconditions.
+	 * @param key - the key.
+	 * @param value - the value to insert.
+	 */
+	private void putInternal(int key, Object value) {
+		try {
+			PUT_METHOD.invoke(handle, key, value);
+		} catch (IllegalArgumentException e) {
+			throw new RuntimeException("Illegal argument.", e);
+		} catch (IllegalAccessException e) {
+			throw new RuntimeException("Cannot access method.", e);
+		} catch (InvocationTargetException e) {
+			throw new RuntimeException("Exception occured in " + PUT_METHOD + " for" + handle, e);
+		}
+	}
+	
+	/**
+	 * Retrieve the value associated with a specific key, or NULL if not found.
+	 * @param key - the integer key.
+	 * @return The associated value, or NULL.
+	 */
+	public Object get(int key) {
+		initializeGetMethod();
+		
+		try {
+			return GET_METHOD.invoke(handle, key);
+		} catch (IllegalArgumentException e) {
+			throw new RuntimeException("Illegal argument.", e);
+		} catch (IllegalAccessException e) {
+			throw new RuntimeException("Cannot access method.", e);
+		} catch (InvocationTargetException e) {
+			throw new RuntimeException("Unable to invoke " + GET_METHOD + " on " + handle, e);
+		}
+	}
+	
+	/**
+	 * Remove a mapping of a key to a value if it is present.
+	 * @param key - the key of the mapping to remove.
+	 * @return TRUE if a key-value pair was removed, FALSE otherwise.
+	 */
+	public boolean remove(int key) {
+		Object prev = get(key);
+		
+		if (prev != null) {
+			putInternal(key, null);
+			return true;
+		}
+		return false;
+	}
+	
+	private void initializePutMethod() {
+		if (PUT_METHOD == null) {
+			// Fairly straight forward
+			PUT_METHOD = FuzzyReflection.fromClass(INT_HASH_MAP).getMethod(
+				FuzzyMethodContract.newBuilder().
+					banModifier(Modifier.STATIC).
+					parameterCount(2).
+					parameterExactType(int.class).
+					parameterExactType(Object.class).
+					build());
+		}
+	}
+	
+	private void initializeGetMethod() {
+		if (GET_METHOD == null) {
+			WrappedIntHashMap temp = WrappedIntHashMap.newMap();
+			String expected = "hello";
+		
+			// Initialize a value
+			temp.put(1, expected);
+			
+			// Determine which method to trust
+			for (Method method : FuzzyReflection.fromClass(INT_HASH_MAP).
+					getMethodListByParameters(Object.class, new Class<?>[] { int.class })) {
+				
+				// Skip static methods
+				if (Modifier.isStatic(method.getModifiers()))
+					continue;
+				
+				try {
+					// See if we found the method we are looking for
+					if (expected.equals(method.invoke(temp.getHandle(), 1))) {
+						GET_METHOD = method;
+						return;
+					}
+				} catch (Exception e) {
+					// Suppress
+				}
+			}
+			throw new IllegalStateException("Unable to find appropriate GET_METHOD for IntHashMap.");
+		}
+	}
+	
+	/**
+	 * Retrieve the underlying IntHashMap object.
+	 * @return The underlying object.
+	 */
+	public Object getHandle() {
+		return handle;
+	}
+}

ProtocolLib/src/test/java/com/comphenix/protocol/utility/StreamSerializerTest.java

@@ -8,6 +8,8 @@ import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
 
+import net.minecraft.server.v1_6_R2.IntHashMap;
+
 import org.bukkit.Material;
 import org.bukkit.craftbukkit.v1_6_R2.inventory.CraftItemFactory;
 import org.bukkit.inventory.ItemStack;
@@ -28,6 +30,11 @@ public class StreamSerializerTest {
 		BukkitInitialization.initializeItemMeta();
 	}
 	
+	@Test
+	public void testMinecraftReflection() {
+		assertEquals(IntHashMap.class, MinecraftReflection.getIntHashMapClass());
+	}
+	
 	@Test
 	public void testSerializer() throws IOException {
 		ItemStack before = new ItemStack(Material.GOLD_AXE);