authlib-injector/src/main/java/moe/yushi/authlibinjector/transform/ClassTransformer.java

/*
 * Copyright (C) 2022  Haowei Wen <yushijinhun@gmail.com> and contributors
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
package moe.yushi.authlibinjector.transform;

import static java.util.Collections.emptyList;
import static moe.yushi.authlibinjector.util.Logging.log;
import static moe.yushi.authlibinjector.util.Logging.Level.DEBUG;
import static moe.yushi.authlibinjector.util.Logging.Level.INFO;
import static moe.yushi.authlibinjector.util.Logging.Level.WARNING;
import static org.objectweb.asm.Opcodes.ACC_INTERFACE;
import static org.objectweb.asm.Opcodes.H_INVOKESTATIC;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Handle;
import moe.yushi.authlibinjector.Config;

public class ClassTransformer implements ClassFileTransformer {

	public final List<TransformUnit> units = new CopyOnWriteArrayList<>();
	public final List<ClassLoadingListener> listeners = new CopyOnWriteArrayList<>();
	public final Set<String> ignores = Collections.newSetFromMap(new ConcurrentHashMap<>());
	public final PerformanceMetrics performanceMetrics = new PerformanceMetrics();

	private static class TransformContextImpl implements TransformContext {

		private final String className;

		public boolean isInterface;
		public boolean modifiedMark;
		public int minVersionMark = -1;
		public int upgradedVersionMark = -1;
		public boolean callbackMetafactoryRequested = false;

		public TransformContextImpl(String className) {
			this.className = className;
		}

		@Override
		public void markModified() {
			modifiedMark = true;
		}

		@Override
		public void requireMinimumClassVersion(int version) {
			if (this.minVersionMark < version) {
				this.minVersionMark = version;
			}
		}

		@Override
		public void upgradeClassVersion(int version) {
			if (this.upgradedVersionMark < version) {
				this.upgradedVersionMark = version;
			}
		}

		@Override
		public Handle acquireCallbackMetafactory() {
			this.callbackMetafactoryRequested = true;
			return new Handle(
					H_INVOKESTATIC,
					className.replace('.', '/'),
					CallbackSupport.METAFACTORY_NAME,
					CallbackSupport.METAFACTORY_SIGNATURE,
					isInterface);
		}
	}

	private static class TransformHandle {

		private final String className;
		private final ClassLoader classLoader;
		private byte[] classBuffer;

		private List<TransformUnit> appliedTransformers;
		private int minVersion = -1;
		private int upgradedVersion = -1;
		private boolean addCallbackMetafactory = false;

		public TransformHandle(ClassLoader classLoader, String className, byte[] classBuffer) {
			this.className = className;
			this.classBuffer = classBuffer;
			this.classLoader = classLoader;
		}

		public void accept(TransformUnit unit) {
			ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_MAXS);
			TransformContextImpl ctx = new TransformContextImpl(className);

			Optional<ClassVisitor> optionalVisitor = unit.transform(classLoader, className, writer, ctx);
			if (optionalVisitor.isPresent()) {
				ClassReader reader = new ClassReader(classBuffer);
				ctx.isInterface = (reader.getAccess() & ACC_INTERFACE) != 0;
				reader.accept(optionalVisitor.get(), 0);
				if (ctx.modifiedMark) {
					log(INFO, "Transformed [" + className + "] with [" + unit + "]");
					if (appliedTransformers == null) {
						appliedTransformers = new ArrayList<>();
					}
					appliedTransformers.add(unit);
					classBuffer = writer.toByteArray();
					if (ctx.minVersionMark > this.minVersion) {
						this.minVersion = ctx.minVersionMark;
					}
					if (ctx.upgradedVersionMark > this.upgradedVersion) {
						this.upgradedVersion = ctx.upgradedVersionMark;
					}
					this.addCallbackMetafactory |= ctx.callbackMetafactoryRequested;
				}
			}
		}

		public Optional<byte[]> finish() {
			if (appliedTransformers == null || appliedTransformers.isEmpty()) {
				return Optional.empty();
			} else {
				if (addCallbackMetafactory) {
					accept(new CallbackMetafactoryTransformer());
				}
				if (minVersion == -1 && upgradedVersion == -1) {
					return Optional.of(classBuffer);
				} else {
					try {
						accept(new ClassVersionTransformUnit(minVersion, upgradedVersion));
						return Optional.of(classBuffer);
					} catch (ClassVersionException e) {
						log(WARNING, "Skipping [" + className + "], " + e.getMessage());
						return Optional.empty();
					}
				}
			}
		}

		public List<TransformUnit> getAppliedTransformers() {
			return appliedTransformers == null ? emptyList() : appliedTransformers;
		}

		public byte[] getFinalResult() {
			return classBuffer;
		}
	}

	@Override
	public byte[] transform(ClassLoader loader, String internalClassName, Class<?> classBeingRedefined, ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
		if (internalClassName != null && classfileBuffer != null) {
			try {
				long t0 = System.nanoTime();

				String className = internalClassName.replace('/', '.');
				for (String prefix : ignores) {
					if (className.startsWith(prefix)) {
						listeners.forEach(it -> it.onClassLoading(loader, className, classfileBuffer, Collections.emptyList()));
						return null;
					}
				}

				TransformHandle handle = new TransformHandle(loader, className, classfileBuffer);
				units.forEach(handle::accept);
				listeners.forEach(it -> it.onClassLoading(loader, className, handle.getFinalResult(), handle.getAppliedTransformers()));

				Optional<byte[]> transformResult = handle.finish();
				if (Config.printUntransformedClass && !transformResult.isPresent()) {
					log(DEBUG, "No transformation is applied to [" + className + "]");
				}

				long t1 = System.nanoTime();

				synchronized (performanceMetrics) {
					performanceMetrics.classesProcessed++;
					performanceMetrics.totalTime += t1 - t0;
				}

				return transformResult.orElse(null);
			} catch (Throwable e) {
				log(WARNING, "Failed to transform [" + internalClassName + "]", e);
			}
		}
		return null;
	}
}