PaperMC/Spigot-API-Patches/0021-Use-ASM-for-event-executors.patch

From bb0950fa863a7f52e3217d936719224d650e224f Mon Sep 17 00:00:00 2001
From: Techcable <Techcable@outlook.com>
Date: Thu, 3 Mar 2016 13:20:33 -0700
Subject: [PATCH] Use ASM for event executors.

Uses method handles for private or static methods.

diff --git a/pom.xml b/pom.xml
index 412a6901..041ae474 100644
--- a/pom.xml
+++ b/pom.xml
@@ -110,6 +110,17 @@
             <version>1.3</version>
             <scope>test</scope>
         </dependency>
+        <!-- ASM -->
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm</artifactId>
+            <version>6.1.1</version>
+        </dependency>
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-commons</artifactId>
+            <version>6.1.1</version>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/src/main/java/com/destroystokyo/paper/event/executor/MethodHandleEventExecutor.java b/src/main/java/com/destroystokyo/paper/event/executor/MethodHandleEventExecutor.java
new file mode 100644
index 00000000..9ff99e3b
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/event/executor/MethodHandleEventExecutor.java
@@ -0,0 +1,40 @@
+package com.destroystokyo.paper.event.executor;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Method;
+
+import org.bukkit.event.Event;
+import org.bukkit.event.EventException;
+import org.bukkit.event.Listener;
+import org.bukkit.plugin.EventExecutor;
+
+public class MethodHandleEventExecutor implements EventExecutor {
+    private final Class<? extends Event> eventClass;
+    private final MethodHandle handle;
+
+    public MethodHandleEventExecutor(Class<? extends Event> eventClass, MethodHandle handle) {
+        this.eventClass = eventClass;
+        this.handle = handle;
+    }
+
+    public MethodHandleEventExecutor(Class<? extends Event> eventClass, Method m) {
+        this.eventClass = eventClass;
+        try {
+            m.setAccessible(true);
+            this.handle = MethodHandles.lookup().unreflect(m);
+        } catch (IllegalAccessException e) {
+            throw new AssertionError("Unable to set accessible", e);
+        }
+    }
+
+    @Override
+    public void execute(Listener listener, Event event) throws EventException {
+        if (!eventClass.isInstance(event)) return;
+        try {
+            handle.invoke(listener, event);
+        } catch (Throwable t) {
+            throw new EventException(t);
+        }
+    }
+}
diff --git a/src/main/java/com/destroystokyo/paper/event/executor/StaticMethodHandleEventExecutor.java b/src/main/java/com/destroystokyo/paper/event/executor/StaticMethodHandleEventExecutor.java
new file mode 100644
index 00000000..f60f0100
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/event/executor/StaticMethodHandleEventExecutor.java
@@ -0,0 +1,39 @@
+package com.destroystokyo.paper.event.executor;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import com.google.common.base.Preconditions;
+
+import org.bukkit.event.Event;
+import org.bukkit.event.EventException;
+import org.bukkit.event.Listener;
+import org.bukkit.plugin.EventExecutor;
+
+public class StaticMethodHandleEventExecutor implements EventExecutor {
+    private final Class<? extends Event> eventClass;
+    private final MethodHandle handle;
+
+    public StaticMethodHandleEventExecutor(Class<? extends Event> eventClass, Method m) {
+        Preconditions.checkArgument(Modifier.isStatic(m.getModifiers()), "Not a static method: %s", m);
+        this.eventClass = eventClass;
+        try {
+            m.setAccessible(true);
+            this.handle = MethodHandles.lookup().unreflect(m);
+        } catch (IllegalAccessException e) {
+            throw new AssertionError("Unable to set accessible", e);
+        }
+    }
+
+    @Override
+    public void execute(Listener listener, Event event) throws EventException {
+        if (!eventClass.isInstance(event)) return;
+        try {
+            handle.invoke(event);
+        } catch (Throwable t) {
+            throw new EventException(t);
+        }
+    }
+}
diff --git a/src/main/java/com/destroystokyo/paper/event/executor/asm/ASMEventExecutorGenerator.java b/src/main/java/com/destroystokyo/paper/event/executor/asm/ASMEventExecutorGenerator.java
new file mode 100644
index 00000000..140cf0ad
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/event/executor/asm/ASMEventExecutorGenerator.java
@@ -0,0 +1,44 @@
+package com.destroystokyo.paper.event.executor.asm;
+
+import java.lang.reflect.Method;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import org.bukkit.plugin.EventExecutor;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Type;
+import org.objectweb.asm.commons.GeneratorAdapter;
+
+import static org.objectweb.asm.Opcodes.*;
+
+public class ASMEventExecutorGenerator {
+    public static byte[] generateEventExecutor(Method m, String name) {
+        ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
+        writer.visit(V1_8, ACC_PUBLIC, name.replace('.', '/'), null, Type.getInternalName(Object.class), new String[] {Type.getInternalName(EventExecutor.class)});
+        // Generate constructor
+        GeneratorAdapter methodGenerator = new GeneratorAdapter(writer.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null), ACC_PUBLIC, "<init>", "()V");
+        methodGenerator.loadThis();
+        methodGenerator.visitMethodInsn(INVOKESPECIAL, Type.getInternalName(Object.class), "<init>", "()V", false); // Invoke the super class (Object) constructor
+        methodGenerator.returnValue();
+        methodGenerator.endMethod();
+        // Generate the execute method
+        methodGenerator = new GeneratorAdapter(writer.visitMethod(ACC_PUBLIC, "execute", "(Lorg/bukkit/event/Listener;Lorg/bukkit/event/Event;)V", null, null), ACC_PUBLIC, "execute", "(Lorg/bukkit/event/Listener;Lorg/bukkit/event/Listener;)V");;
+        methodGenerator.loadArg(0);
+        methodGenerator.checkCast(Type.getType(m.getDeclaringClass()));
+        methodGenerator.loadArg(1);
+        methodGenerator.checkCast(Type.getType(m.getParameterTypes()[0]));
+        methodGenerator.visitMethodInsn(m.getDeclaringClass().isInterface() ? INVOKEINTERFACE : INVOKEVIRTUAL, Type.getInternalName(m.getDeclaringClass()), m.getName(), Type.getMethodDescriptor(m), m.getDeclaringClass().isInterface());
+        if (m.getReturnType() != void.class) {
+            methodGenerator.pop();
+        }
+        methodGenerator.returnValue();
+        methodGenerator.endMethod();
+        writer.visitEnd();
+        return writer.toByteArray();
+    }
+
+    public static AtomicInteger NEXT_ID = new AtomicInteger(1);
+    public static String generateName() {
+        int id = NEXT_ID.getAndIncrement();
+        return "com.destroystokyo.paper.event.executor.asm.generated.GeneratedEventExecutor" + id;
+    }
+}
diff --git a/src/main/java/com/destroystokyo/paper/event/executor/asm/ClassDefiner.java b/src/main/java/com/destroystokyo/paper/event/executor/asm/ClassDefiner.java
new file mode 100644
index 00000000..6941d9fb
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/event/executor/asm/ClassDefiner.java
@@ -0,0 +1,32 @@
+package com.destroystokyo.paper.event.executor.asm;
+
+import com.destroystokyo.paper.utils.UnsafeUtils;
+
+public interface ClassDefiner {
+
+    /**
+     * Returns if the defined classes can bypass access checks
+     *
+     * @return if classes bypass access checks
+     */
+    public default boolean isBypassAccessChecks() {
+        return false;
+    }
+
+    /**
+     * Define a class
+     *
+     * @param parentLoader the parent classloader
+     * @param name         the name of the class
+     * @param data         the class data to load
+     * @return the defined class
+     * @throws ClassFormatError     if the class data is invalid
+     * @throws NullPointerException if any of the arguments are null
+     */
+    public Class<?> defineClass(ClassLoader parentLoader, String name, byte[] data);
+
+    public static ClassDefiner getInstance() {
+        return SafeClassDefiner.INSTANCE;
+    }
+
+}
diff --git a/src/main/java/com/destroystokyo/paper/event/executor/asm/SafeClassDefiner.java b/src/main/java/com/destroystokyo/paper/event/executor/asm/SafeClassDefiner.java
new file mode 100644
index 00000000..1473ff8c
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/event/executor/asm/SafeClassDefiner.java
@@ -0,0 +1,63 @@
+package com.destroystokyo.paper.event.executor.asm;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+import com.google.common.base.Preconditions;
+
+import com.google.common.collect.MapMaker;
+import org.objectweb.asm.Type;
+
+public class SafeClassDefiner implements ClassDefiner {
+    /* default */ static final SafeClassDefiner INSTANCE = new SafeClassDefiner();
+
+    private SafeClassDefiner() {}
+
+    private final ConcurrentMap<ClassLoader, GeneratedClassLoader> loaders = new MapMaker().weakKeys().makeMap();
+
+    @Override
+    public Class<?> defineClass(ClassLoader parentLoader, String name, byte[] data) {
+        GeneratedClassLoader loader = loaders.computeIfAbsent(parentLoader, GeneratedClassLoader::new);
+        synchronized (loader.getClassLoadingLock(name)) {
+            Preconditions.checkState(!loader.hasClass(name), "%s already defined", name);
+            Class<?> c = loader.define(name, data);
+            assert c.getName().equals(name);
+            return c;
+        }
+    }
+
+    private static class GeneratedClassLoader extends ClassLoader {
+        static {
+            ClassLoader.registerAsParallelCapable();
+        }
+
+        protected GeneratedClassLoader(ClassLoader parent) {
+            super(parent);
+        }
+
+        private Class<?> define(String name, byte[] data) {
+            synchronized (getClassLoadingLock(name)) {
+                assert !hasClass(name);
+                Class<?> c = defineClass(name, data, 0, data.length);
+                resolveClass(c);
+                return c;
+            }
+        }
+
+        @Override
+        public Object getClassLoadingLock(String name) {
+            return super.getClassLoadingLock(name);
+        }
+
+        public boolean hasClass(String name) {
+            synchronized (getClassLoadingLock(name)) {
+                try {
+                    Class.forName(name);
+                    return true;
+                } catch (ClassNotFoundException e) {
+                    return false;
+                }
+            }
+        }
+    }
+}
diff --git a/src/main/java/com/destroystokyo/paper/utils/UnsafeUtils.java b/src/main/java/com/destroystokyo/paper/utils/UnsafeUtils.java
new file mode 100644
index 00000000..62acbf82
--- /dev/null
+++ b/src/main/java/com/destroystokyo/paper/utils/UnsafeUtils.java
@@ -0,0 +1,33 @@
+package com.destroystokyo.paper.utils;
+
+import sun.misc.Unsafe;
+
+import java.lang.reflect.Field;
+
+public class UnsafeUtils {
+    private UnsafeUtils() {}
+
+    private static final Unsafe UNSAFE;
+    static {
+        Unsafe unsafe;
+        try {
+            Class c = Class.forName("sun.misc.Unsafe");
+            Field f = c.getDeclaredField("theUnsafe");
+            f.setAccessible(true);
+            unsafe = (Unsafe) f.get(null);
+        } catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
+            unsafe = null;
+        } catch (IllegalAccessException e) {
+            throw new AssertionError(e);
+        }
+        UNSAFE = unsafe;
+    }
+
+    public static boolean isUnsafeSupported() {
+        return UNSAFE != null;
+    }
+
+    public static Unsafe getUnsafe() {
+        return UNSAFE;
+    }
+}
diff --git a/src/main/java/org/bukkit/plugin/EventExecutor.java b/src/main/java/org/bukkit/plugin/EventExecutor.java
index 3b2c99ea..b45b6c1c 100644
--- a/src/main/java/org/bukkit/plugin/EventExecutor.java
+++ b/src/main/java/org/bukkit/plugin/EventExecutor.java
@@ -4,9 +4,81 @@ import org.bukkit.event.Event;
 import org.bukkit.event.EventException;
 import org.bukkit.event.Listener;
 
+// Paper start
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+import java.util.HashMap;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+import java.util.function.Function;
+
+import com.destroystokyo.paper.event.executor.MethodHandleEventExecutor;
+import com.destroystokyo.paper.event.executor.StaticMethodHandleEventExecutor;
+import com.destroystokyo.paper.event.executor.asm.ASMEventExecutorGenerator;
+import com.destroystokyo.paper.event.executor.asm.ClassDefiner;
+import com.google.common.base.Preconditions;
+// Paper end
+
 /**
  * Interface which defines the class for event call backs to plugins
  */
 public interface EventExecutor {
     public void execute(Listener listener, Event event) throws EventException;
+
+    // Paper start
+    ConcurrentMap<Method, Class<? extends EventExecutor>> eventExecutorMap = new ConcurrentHashMap<Method, Class<? extends EventExecutor>>() {
+        @Override
+        public Class<? extends EventExecutor> computeIfAbsent(Method key, Function<? super Method, ? extends Class<? extends EventExecutor>> mappingFunction) {
+            Class<? extends EventExecutor> executorClass = get(key);
+            if (executorClass != null)
+                return executorClass;
+
+            //noinspection SynchronizationOnLocalVariableOrMethodParameter
+            synchronized (key) {
+                executorClass = get(key);
+                if (executorClass != null)
+                    return executorClass;
+
+                return super.computeIfAbsent(key, mappingFunction);
+            }
+        }
+    };
+
+    public static EventExecutor create(Method m, Class<? extends Event> eventClass) {
+        Preconditions.checkNotNull(m, "Null method");
+        Preconditions.checkArgument(m.getParameterCount() != 0, "Incorrect number of arguments %s", m.getParameterCount());
+        Preconditions.checkArgument(m.getParameterTypes()[0] == eventClass, "First parameter %s doesn't match event class %s", m.getParameterTypes()[0], eventClass);
+        ClassDefiner definer = ClassDefiner.getInstance();
+        if (Modifier.isStatic(m.getModifiers())) {
+            return new StaticMethodHandleEventExecutor(eventClass, m);
+        } else if (definer.isBypassAccessChecks() || Modifier.isPublic(m.getDeclaringClass().getModifiers()) && Modifier.isPublic(m.getModifiers())) {
+            // get the existing generated EventExecutor class for the Method or generate one
+            Class<? extends EventExecutor> executorClass = eventExecutorMap.computeIfAbsent(m, (__) -> {
+                String name = ASMEventExecutorGenerator.generateName();
+                byte[] classData = ASMEventExecutorGenerator.generateEventExecutor(m, name);
+                return definer.defineClass(m.getDeclaringClass().getClassLoader(), name, classData).asSubclass(EventExecutor.class);
+            });
+
+            try {
+                EventExecutor asmExecutor = executorClass.newInstance();
+                // Define a wrapper to conform to bukkit stupidity (passing in events that don't match and wrapper exception)
+                return new EventExecutor() {
+                    @Override
+                    public void execute(Listener listener, Event event) throws EventException {
+                        if (!eventClass.isInstance(event)) return;
+                        try {
+                            asmExecutor.execute(listener, event);
+                        } catch (Exception e) {
+                            throw new EventException(e);
+                        }
+                    }
+                };
+            } catch (InstantiationException | IllegalAccessException e) {
+                throw new AssertionError("Unable to initialize generated event executor", e);
+            }
+        } else {
+            return new MethodHandleEventExecutor(eventClass, m);
+        }
+    }
+    // Paper end
 }
diff --git a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
index bf972302..77207f14 100644
--- a/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
+++ b/src/main/java/org/bukkit/plugin/java/JavaPluginLoader.java
@@ -290,20 +290,7 @@ public final class JavaPluginLoader implements PluginLoader {
                 }
             }
 
-            EventExecutor executor = new co.aikar.timings.TimedEventExecutor(new EventExecutor() { // Spigot
-                public void execute(Listener listener, Event event) throws EventException {
-                    try {
-                        if (!eventClass.isAssignableFrom(event.getClass())) {
-                            return;
-                        }
-                        method.invoke(listener, event);
-                    } catch (InvocationTargetException ex) {
-                        throw new EventException(ex.getCause());
-                    } catch (Throwable t) {
-                        throw new EventException(t);
-                    }
-                }
-            }, plugin, method, eventClass); // Spigot
+            EventExecutor executor = new co.aikar.timings.TimedEventExecutor(EventExecutor.create(method, eventClass), plugin, method, eventClass); // Spigot // Paper - Use factory method `EventExecutor.create()`
             if (false) { // Spigot - RL handles useTimings check now
                 eventSet.add(new TimedRegisteredListener(listener, executor, eh.priority(), plugin, eh.ignoreCancelled()));
             } else {
-- 
2.20.1