feat: got the patcher working*

*only in unobfuscated environment, and I did it using hacky awfulness that will be deleted as soon as possible.

4 files changed, 793 insertions, 33 deletions

diff --git a/src/main/java/bscv/asm/BoSCoVicinoLoader.java b/src/main/java/bscv/asm/BoSCoVicinoLoader.java
index 77d5f6e..15a2bbf 100644
--- a/src/main/java/bscv/asm/BoSCoVicinoLoader.java
+++ b/src/main/java/bscv/asm/BoSCoVicinoLoader.java
@@ -1,27 +1,33 @@
 package bscv.asm;
 
-import java.io.IOException;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-import java.util.*;
-import java.util.stream.Collectors;
-
 import bscv.asm.api.AnnotationChecker;
+import bscv.asm.util.ClassPath22;
 import bscv.asm.api.annotations.Inject;
 import bscv.asm.api.annotations.Patch;
 import com.google.common.collect.HashMultimap;
+import cpw.mods.modlauncher.api.INameMappingService;
+import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
+import net.minecraftforge.fml.common.ObfuscationReflectionHelper;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.Type;
-
-import cpw.mods.modlauncher.serviceapi.ILaunchPluginService;
 import org.objectweb.asm.tree.ClassNode;
 import org.objectweb.asm.tree.MethodNode;
 
+import javax.annotation.Nullable;
+import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.EnumSet;
+import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
+
 public class BoSCoVicinoLoader implements ILaunchPluginService {
 
-	public static final String NAME = "boscovicino_asm"; //temp name
+	public static final String NAME = "boscovicino_asm"; //TODO: temp name
 	public static final Logger LOGGER = LogManager.getLogger("BoSCoVicinoASM");
 
 	private static final EnumSet<Phase> YAY = EnumSet.of(Phase.BEFORE);
@@ -30,6 +36,7 @@ public class BoSCoVicinoLoader implements ILaunchPluginService {
 	private static final HashMultimap<String, Class<?>> patchClasses = HashMultimap.create();
 
 	public BoSCoVicinoLoader() {
+		loadPatchesPozzed();
 		LOGGER.info("BoSCoVicinoLoader instantiated successfully!");
 	}
 
@@ -40,9 +47,6 @@ public class BoSCoVicinoLoader implements ILaunchPluginService {
 
 	@Override
 	public EnumSet<Phase> handlesClass(Type classType, final boolean isEmpty) {
-		//if(!isEmpty && shouldHandle(classType))
-		//	LOGGER.info("CLAZZ >>> {}", classType.getClassName());
-		//return NAY;
 		throw new IllegalStateException("Outdated ModLauncher"); //mixin does it
 	}
 
@@ -50,99 +54,155 @@ public class BoSCoVicinoLoader implements ILaunchPluginService {
 	public EnumSet<Phase> handlesClass(Type classType, final boolean isEmpty, final String reason) {
 		if(isEmpty) return NAY;
 		String name = classType.getClassName();
-		if(name.startsWith("net.minecraft.") || name.indexOf('.') == -1)
+		if(name.startsWith("net.minecraft.") || name.indexOf('.') == -1) {
+			LOGGER.debug("Marked {} as to-be-handled", classType.getClassName());
 			return YAY;
+		} else return NAY;
+		/* TODO: either bring back or delete this (probably the latter)
 		else {
 			try {
 				if(hasAnnotation(name)) {
 					Class<?> patch = Class.forName(name);
-					patchClasses.put(Type.getDescriptor(patch.getAnnotation(Patch.class).value()), patch);
-					return YAY;
+					//patchClasses.put(patch.getAnnotation(Patch.class).value(), patch);
+					//LOGGER.info("Found patch class {}", patch.getName());
 				}
 			} catch(IOException | ClassNotFoundException e) {
 				LOGGER.debug("Could not load {}", name);
 			}
 			return NAY;
-		}
+		} */
 	}
 
 	@Override
 	public int processClassWithFlags(Phase phase, ClassNode classNode, Type classType, String reason) {
-		if(patchClasses.containsKey(classType.getDescriptor())) {
+		LOGGER.debug("Processing class {} in phase {} of {}", classType.getClassName(), phase.name(), reason);
+		if(patchClasses.containsKey(classType.getClassName())) {
+			LOGGER.info("Found class with descriptor {} among the patches", classType.getClassName());
 			//can have multiple patches working on same class
 			//each of these classes may attempt to patch a method one or more times
 			Set<String> classMethodNames = classNode.methods
 				.stream()
-				.map(m -> m.name)
+				.map(m -> deobfuscator(m.name))
 				.collect(Collectors.toSet());
 			Set<String> classMethodDescriptors = classNode.methods
 				.stream()
 				.map(m -> m.desc)
 				.collect(Collectors.toSet());
-			Set<Class<?>> relevantPatches = patchClasses.get(classType.getDescriptor());
 			HashMultimap<Object, Method> patches = HashMultimap.create();
-			relevantPatches
+			patchClasses
+				.get(classType.getClassName())
 				.forEach(p -> {
 					Set<Method> injectors =
 						getInjectorsInPatch(p)
 							.stream()
 							.filter(m -> {
 								Inject a = m.getAnnotation(Inject.class);
-								return
-									classMethodNames.contains(a.methodName())
+								LOGGER.info("Found {} injector for method {}{}", m.getName(), a.methodName(), descriptorBuilder(a.returnType(), a.parameters()));
+								return classMethodNames.contains(a.methodName())
 										&& classMethodDescriptors.contains(descriptorBuilder(a.returnType(), a.parameters()));
 							})
 							.collect(Collectors.toSet());
 					if(!injectors.isEmpty()) {
 						try {
 							patches.putAll(p.newInstance(), injectors);
+							StringBuilder sb = new StringBuilder();
+							for(Method i : injectors)
+								sb.append(i.getName()).append(",");
+							LOGGER.info("Stored patch {} with injectors {}", p, sb.toString());
 						} catch(InstantiationException | IllegalAccessException e) {
-							throw new RuntimeException(e); //todo: better catch
+							LOGGER.error("Something went wrong while instantiating patch {}", p);
+							throw new RuntimeException(e); //todo: better error handling
 						}
 					}
 				});
-			if(patches.isEmpty())
+			if(patches.isEmpty()) {
+				LOGGER.info("No valid patches found for {}!", classNode.name.replace('/', '.'));
 				return ComputeFlags.NO_REWRITE;
-			else {
+			} else {
 				boolean success = false;
 				for(Object p : patches.keys())
 					for(Method m : patches.get(p))
-						success = success || processInjector(classNode, p, m);
+						success = processInjector(classNode, p, m) || success;
+				LOGGER.info("Altered class {}", classNode.name);
 				return success ? ComputeFlags.COMPUTE_FRAMES : ComputeFlags.NO_REWRITE; //todo: is this the right flag?
 			}
 		} else return ComputeFlags.NO_REWRITE;
 	}
 
-	private boolean hasAnnotation(String name) throws IOException {
+	/* TODO:	Get fucking rid of this!
+	 *			This method is pure evil. It scans the JAR and forcefully loads the patches.
+	 *			Sure, it works, but it makes it impossible to split Patch Framework and client. It's
+	 * 			also very slow.
+	 *			Cherry on top: ClassPath in Guava 21 is broken. My solution was to shamelessly paste
+	 * 			the version from Guava 22 as ClassPath22. License-wise there shouldn't be any problem,
+	 * 			but I have no intention of keeping it. It's only used here, and this method needs to
+	 * 			go as soon as humanly possible. Don't worry, I'm not bloating your precious codebase.
+	 * 			P.S.: Yes, that's why your shot at dynloading Modules didn't work.
+	 **/
+	private static void loadPatchesPozzed() {
+		try {
+			ClassPath22.from(BoSCoVicinoLoader.class.getClassLoader())
+				.getAllClasses()
+				.stream()
+				.filter(ci -> {
+					try {
+						return hasAnnotation(ci.getName());
+					} catch(IOException e) {
+						throw new RuntimeException(e);
+					}
+				})
+				.map(ClassPath22.ClassInfo::load)
+				.forEach(patch -> {
+					patchClasses.put(patch.getAnnotation(Patch.class).value(), patch);
+					LOGGER.info("Found patch class {}", patch.getName());
+				});
+		} catch(IOException e) {
+			e.printStackTrace();
+		}
+	}
+
+	private static boolean hasAnnotation(String name) throws IOException {
 		ClassReader cr = new ClassReader(name);
 		AnnotationChecker ac = new AnnotationChecker(Patch.class);
 		cr.accept(ac, 0);
 		return ac.isAnnotationPresent();
 	}
 
-	private Set<Method> getInjectorsInPatch(Class<?> patch) {
+	private static Set<Method> getInjectorsInPatch(Class<?> patch) {
 		return Arrays.stream(patch.getDeclaredMethods())
 				.filter(m -> m.isAnnotationPresent(Inject.class))
 				.collect(Collectors.toSet());
 	}
 
-	public static String descriptorBuilder(Class<?> returnType, Class<?>[] parameters) {
+	public static String descriptorBuilder(@Nullable Class<?> returnType, Class<?> ... parameters) {
 		StringBuilder desc = new StringBuilder("(");
 		for(Class<?> p : parameters)
 			desc.append(Type.getDescriptor(p));
 		desc.append(")");
-		desc.append(Type.getDescriptor(returnType));
+		if(returnType != null)
+			desc.append(Type.getDescriptor(returnType));
 		return desc.toString();
 	}
 
-	private boolean processInjector(ClassNode target, Object patch, Method injector) {
+	public static String descriptorBuilder(Class<?>[] parameters) {
+		return descriptorBuilder(null, parameters);
+	}
+
+	private static String deobfuscator(String srg) {
+		/* FIXME: this will only work in client env (runClient task)
+		    Find a different way to deobf searge names or try to circumvent
+		    this step altogether (serve already deobfed names?) */
+		return ObfuscationReflectionHelper.remapName(INameMappingService.Domain.METHOD, srg);
+	}
+
+	private static boolean processInjector(ClassNode target, Object patch, Method injector) {
 		//get relevant method from target
 		Optional<MethodNode> targetMethod =
 			target.methods
 				.stream()
 				.filter(m -> {
 					Inject a = injector.getAnnotation(Inject.class);
-					return m.name.equals(a.methodName()) && m.desc.equals(descriptorBuilder(a.returnType(), a.parameters()));
+					return m.name.equals(a.methodName()) && m.desc.startsWith(descriptorBuilder(a.parameters()));
 				})
 				.findAny(); //there can literally only be one so this is safe and more efficient than findFirst
 
diff --git a/src/main/java/bscv/asm/api/annotations/Patch.java b/src/main/java/bscv/asm/api/annotations/Patch.java
index 4685845..2b6963f 100644
--- a/src/main/java/bscv/asm/api/annotations/Patch.java
+++ b/src/main/java/bscv/asm/api/annotations/Patch.java
@@ -8,5 +8,5 @@ import java.lang.annotation.Target;
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.RUNTIME)
 public @interface Patch {
-	Class<?> value();
+	String value();
 }
diff --git a/src/main/java/bscv/asm/patches/TestPatch.java b/src/main/java/bscv/asm/patches/TestPatch.java
new file mode 100644
index 0000000..b1454ab
--- /dev/null
+++ b/src/main/java/bscv/asm/patches/TestPatch.java
@@ -0,0 +1,30 @@
+package bscv.asm.patches;
+
+import bscv.asm.api.annotations.Inject;
+import bscv.asm.api.annotations.Patch;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.InsnList;
+import org.objectweb.asm.tree.InsnNode;
+import org.objectweb.asm.tree.MethodNode;
+
+/**
+ * When working as intended, this patch will crash the game
+ * as soon it finished loading with a NegativeArraySizeException.
+ */
+@Patch("net.minecraft.client.Minecraft")
+public class TestPatch implements Opcodes {
+
+	@Inject(methodName = "tick", returnType = void.class, parameters = {}, description = "Test injection!")
+	public void inject(MethodNode main) {
+		InsnList insnList = new InsnList();
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		insnList.add(new InsnNode(POP));
+		main.instructions.insert(insnList);
+	}
+}
diff --git a/src/main/java/bscv/asm/util/ClassPath22.java b/src/main/java/bscv/asm/util/ClassPath22.java
new file mode 100644
index 0000000..0edc825
--- /dev/null
+++ b/src/main/java/bscv/asm/util/ClassPath22.java
@@ -0,0 +1,670 @@
+package bscv.asm.util;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.base.StandardSystemProperty.JAVA_CLASS_PATH;
+import static com.google.common.base.StandardSystemProperty.PATH_SEPARATOR;
+import static java.util.logging.Level.WARNING;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.CharMatcher;
+import com.google.common.base.Splitter;
+import com.google.common.collect.FluentIterable;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Maps;
+import com.google.common.io.ByteSource;
+import com.google.common.io.CharSource;
+import com.google.common.io.Resources;
+import com.google.common.reflect.Reflection;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.URISyntaxException;
+import java.net.URL;
+import java.net.URLClassLoader;
+import java.nio.charset.Charset;
+import java.util.Enumeration;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+import java.util.jar.Attributes;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
+import java.util.jar.Manifest;
+import java.util.logging.Logger;
+import javax.annotation.CheckForNull;
+
+/**
+ * Scans the source of a {@link ClassLoader} and finds all loadable classes and resources.
+ *
+ * <h2>Prefer <a href="https://github.com/classgraph/classgraph/wiki">ClassGraph</a> over {@code
+ * ClassPath22}</h2>
+ *
+ * <p>We recommend using <a href="https://github.com/classgraph/classgraph/wiki">ClassGraph</a>
+ * instead of {@code ClassPath22}. ClassGraph improves upon {@code ClassPath22} in several ways,
+ * including addressing many of its limitations. Limitations of {@code ClassPath22} include:
+ *
+ * <ul>
+ *   <li>It looks only for files and JARs in URLs available from {@link URLClassLoader} instances or
+ *       the {@linkplain ClassLoader#getSystemClassLoader() system class loader}. This means it does
+ *       not look for classes in the <i>module path</i>.
+ *   <li>It understands only {@code file:} URLs. This means that it does not understand <a
+ *       href="https://openjdk.java.net/jeps/220">{@code jrt:/} URLs</a>, among <a
+ *       href="https://github.com/classgraph/classgraph/wiki/Classpath-specification-mechanisms">others</a>.
+ *   <li>It does not know how to look for classes when running under an Android VM. (ClassGraph does
+ *       not support this directly, either, but ClassGraph documents how to <a
+ *       href="https://github.com/classgraph/classgraph/wiki/Build-Time-Scanning">perform build-time
+ *       classpath scanning and make the results available to an Android app</a>.)
+ *   <li>Like all of Guava, it is not tested under Windows. We have gotten <a
+ *       href="https://github.com/google/guava/issues/2130">a report of a specific bug under
+ *       Windows</a>.
+ *   <li>It <a href="https://github.com/google/guava/issues/2712">returns only one resource for a
+ *       given path</a>, even if resources with that path appear in multiple jars or directories.
+ *   <li>It assumes that <a href="https://github.com/google/guava/issues/3349">any class with a
+ *       {@code $} in its name is a nested class</a>.
+ * </ul>
+ *
+ * <h2>{@code ClassPath22} and symlinks</h2>
+ *
+ * <p>In the case of directory classloaders, symlinks are supported but cycles are not traversed.
+ * This guarantees discovery of each <em>unique</em> loadable resource. However, not all possible
+ * aliases for resources on cyclic paths will be listed.
+ *
+ * @author Ben Yu
+ * @since 14.0
+ */
+public final class ClassPath22 {
+	private static final Logger logger = Logger.getLogger(ClassPath22.class.getName());
+
+	/** Separator for the Class-Path manifest attribute value in jar files. */
+	private static final Splitter CLASS_PATH_ATTRIBUTE_SEPARATOR =
+		Splitter.on(" ").omitEmptyStrings();
+
+	private static final String CLASS_FILE_NAME_EXTENSION = ".class";
+
+	private final ImmutableSet<ResourceInfo> resources;
+
+	private ClassPath22(ImmutableSet<ResourceInfo> resources) {
+		this.resources = resources;
+	}
+
+	/**
+	 * Returns a {@code ClassPath22} representing all classes and resources loadable from {@code
+	 * classloader} and its ancestor class loaders.
+	 *
+	 * <p><b>Warning:</b> {@code ClassPath22} can find classes and resources only from:
+	 *
+	 * <ul>
+	 *   <li>{@link URLClassLoader} instances' {@code file:} URLs
+	 *   <li>the {@linkplain ClassLoader#getSystemClassLoader() system class loader}. To search the
+	 *       system class loader even when it is not a {@link URLClassLoader} (as in Java 9), {@code
+	 *       ClassPath22} searches the files from the {@code java.class.path} system property.
+	 * </ul>
+	 *
+	 * @throws IOException if the attempt to read class path resources (jar files or directories)
+	 *     failed.
+	 */
+	public static ClassPath22 from(ClassLoader classloader) throws IOException {
+		ImmutableSet<LocationInfo> locations = locationsFrom(classloader);
+
+		// Add all locations to the scanned set so that in a classpath [jar1, jar2], where jar1 has a
+		// manifest with Class-Path pointing to jar2, we won't scan jar2 twice.
+		Set<File> scanned = new HashSet<>();
+		for (LocationInfo location : locations) {
+			scanned.add(location.file());
+		}
+
+		// Scan all locations
+		ImmutableSet.Builder<ResourceInfo> builder = ImmutableSet.builder();
+		for (LocationInfo location : locations) {
+			builder.addAll(location.scanResources(scanned));
+		}
+		return new ClassPath22(builder.build());
+	}
+
+	/**
+	 * Returns all resources loadable from the current class path, including the class files of all
+	 * loadable classes but excluding the "META-INF/MANIFEST.MF" file.
+	 */
+	public ImmutableSet<ResourceInfo> getResources() {
+		return resources;
+	}
+
+	/**
+	 * Returns all classes loadable from the current class path.
+	 *
+	 * @since 16.0
+	 */
+	public ImmutableSet<ClassInfo> getAllClasses() {
+		return FluentIterable.from(resources).filter(ClassInfo.class).toSet();
+	}
+
+	/**
+	 * Returns all top level classes loadable from the current class path. Note that "top-level-ness"
+	 * is determined heuristically by class name (see {@link ClassInfo#isTopLevel}).
+	 */
+	public ImmutableSet<ClassInfo> getTopLevelClasses() {
+		return FluentIterable.from(resources)
+			.filter(ClassInfo.class)
+			.filter(ClassInfo::isTopLevel)
+			.toSet();
+	}
+
+	/** Returns all top level classes whose package name is {@code packageName}. */
+	public ImmutableSet<ClassInfo> getTopLevelClasses(String packageName) {
+		checkNotNull(packageName);
+		ImmutableSet.Builder<ClassInfo> builder = ImmutableSet.builder();
+		for (ClassInfo classInfo : getTopLevelClasses()) {
+			if (classInfo.getPackageName().equals(packageName)) {
+				builder.add(classInfo);
+			}
+		}
+		return builder.build();
+	}
+
+	/**
+	 * Returns all top level classes whose package name is {@code packageName} or starts with {@code
+	 * packageName} followed by a '.'.
+	 */
+	public ImmutableSet<ClassInfo> getTopLevelClassesRecursive(String packageName) {
+		checkNotNull(packageName);
+		String packagePrefix = packageName + '.';
+		ImmutableSet.Builder<ClassInfo> builder = ImmutableSet.builder();
+		for (ClassInfo classInfo : getTopLevelClasses()) {
+			if (classInfo.getName().startsWith(packagePrefix)) {
+				builder.add(classInfo);
+			}
+		}
+		return builder.build();
+	}
+
+	/**
+	 * Represents a class path resource that can be either a class file or any other resource file
+	 * loadable from the class path.
+	 *
+	 * @since 14.0
+	 */
+	public static class ResourceInfo {
+		private final File file;
+		private final String resourceName;
+
+		final ClassLoader loader;
+
+		static ResourceInfo of(File file, String resourceName, ClassLoader loader) {
+			if (resourceName.endsWith(CLASS_FILE_NAME_EXTENSION)) {
+				return new ClassInfo(file, resourceName, loader);
+			} else {
+				return new ResourceInfo(file, resourceName, loader);
+			}
+		}
+
+		ResourceInfo(File file, String resourceName, ClassLoader loader) {
+			this.file = checkNotNull(file);
+			this.resourceName = checkNotNull(resourceName);
+			this.loader = checkNotNull(loader);
+		}
+
+		/**
+		 * Returns the url identifying the resource.
+		 *
+		 * <p>See {@link ClassLoader#getResource}
+		 *
+		 * @throws NoSuchElementException if the resource cannot be loaded through the class loader,
+		 *     despite physically existing in the class path.
+		 */
+		public final URL url() {
+			URL url = loader.getResource(resourceName);
+			if (url == null) {
+				throw new NoSuchElementException(resourceName);
+			}
+			return url;
+		}
+
+		/**
+		 * Returns a {@link ByteSource} view of the resource from which its bytes can be read.
+		 *
+		 * @throws NoSuchElementException if the resource cannot be loaded through the class loader,
+		 *     despite physically existing in the class path.
+		 * @since 20.0
+		 */
+		public final ByteSource asByteSource() {
+			return Resources.asByteSource(url());
+		}
+
+		/**
+		 * Returns a {@link CharSource} view of the resource from which its bytes can be read as
+		 * characters decoded with the given {@code charset}.
+		 *
+		 * @throws NoSuchElementException if the resource cannot be loaded through the class loader,
+		 *     despite physically existing in the class path.
+		 * @since 20.0
+		 */
+		public final CharSource asCharSource(Charset charset) {
+			return Resources.asCharSource(url(), charset);
+		}
+
+		/** Returns the fully qualified name of the resource. Such as "com/mycomp/foo/bar.txt". */
+		public final String getResourceName() {
+			return resourceName;
+		}
+
+		/** Returns the file that includes this resource. */
+		final File getFile() {
+			return file;
+		}
+
+		@Override
+		public int hashCode() {
+			return resourceName.hashCode();
+		}
+
+		@Override
+		public boolean equals(@CheckForNull Object obj) {
+			if (obj instanceof ResourceInfo) {
+				ResourceInfo that = (ResourceInfo) obj;
+				return resourceName.equals(that.resourceName) && loader == that.loader;
+			}
+			return false;
+		}
+
+		// Do not change this arbitrarily. We rely on it for sorting ResourceInfo.
+		@Override
+		public String toString() {
+			return resourceName;
+		}
+	}
+
+	/**
+	 * Represents a class that can be loaded through {@link #load}.
+	 *
+	 * @since 14.0
+	 */
+	public static final class ClassInfo extends ResourceInfo {
+		private final String className;
+
+		ClassInfo(File file, String resourceName, ClassLoader loader) {
+			super(file, resourceName, loader);
+			this.className = getClassName(resourceName);
+		}
+
+		/**
+		 * Returns the package name of the class, without attempting to load the class.
+		 *
+		 * <p>Behaves similarly to {@code class.getPackage().}{@link Package#getName() getName()} but
+		 * does not require the class (or package) to be loaded.
+		 *
+		 * <p>But note that this method may behave differently for a class in the default package: For
+		 * such classes, this method always returns an empty string. But under some version of Java,
+		 * {@code class.getPackage().getName()} produces a {@code NullPointerException} because {@code
+		 * class.getPackage()} returns {@code null}.
+		 */
+		public String getPackageName() {
+			return Reflection.getPackageName(className);
+		}
+
+		/**
+		 * Returns the simple name of the underlying class as given in the source code.
+		 *
+		 * <p>Behaves similarly to {@link Class#getSimpleName()} but does not require the class to be
+		 * loaded.
+		 *
+		 * <p>But note that this class uses heuristics to identify the simple name. See a related
+		 * discussion in <a href="https://github.com/google/guava/issues/3349">issue 3349</a>.
+		 */
+		public String getSimpleName() {
+			int lastDollarSign = className.lastIndexOf('$');
+			if (lastDollarSign != -1) {
+				String innerClassName = className.substring(lastDollarSign + 1);
+				// local and anonymous classes are prefixed with number (1,2,3...), anonymous classes are
+				// entirely numeric whereas local classes have the user supplied name as a suffix
+				return CharMatcher.inRange('0', '9').trimLeadingFrom(innerClassName);
+			}
+			String packageName = getPackageName();
+			if (packageName.isEmpty()) {
+				return className;
+			}
+
+			// Since this is a top level class, its simple name is always the part after package name.
+			return className.substring(packageName.length() + 1);
+		}
+
+		/**
+		 * Returns the fully qualified name of the class.
+		 *
+		 * <p>Behaves identically to {@link Class#getName()} but does not require the class to be
+		 * loaded.
+		 */
+		public String getName() {
+			return className;
+		}
+
+		/**
+		 * Returns true if the class name "looks to be" top level (not nested), that is, it includes no
+		 * '$' in the name. This method may return false for a top-level class that's intentionally
+		 * named with the '$' character. If this is a concern, you could use {@link #load} and then
+		 * check on the loaded {@link Class} object instead.
+		 *
+		 * @since 30.1
+		 */
+		public boolean isTopLevel() {
+			return className.indexOf('$') == -1;
+		}
+
+		/**
+		 * Loads (but doesn't link or initialize) the class.
+		 *
+		 * @throws LinkageError when there were errors in loading classes that this class depends on.
+		 *     For example, {@link NoClassDefFoundError}.
+		 */
+		public Class<?> load() {
+			try {
+				return loader.loadClass(className);
+			} catch (ClassNotFoundException e) {
+				// Shouldn't happen, since the class name is read from the class path.
+				throw new IllegalStateException(e);
+			}
+		}
+
+		@Override
+		public String toString() {
+			return className;
+		}
+	}
+
+	/**
+	 * Returns all locations that {@code classloader} and parent loaders load classes and resources
+	 * from. Callers can {@linkplain LocationInfo#scanResources scan} individual locations selectively
+	 * or even in parallel.
+	 */
+	static ImmutableSet<LocationInfo> locationsFrom(ClassLoader classloader) {
+		ImmutableSet.Builder<LocationInfo> builder = ImmutableSet.builder();
+		for (Map.Entry<File, ClassLoader> entry : getClassPathEntries(classloader).entrySet()) {
+			builder.add(new LocationInfo(entry.getKey(), entry.getValue()));
+		}
+		return builder.build();
+	}
+
+	/**
+	 * Represents a single location (a directory or a jar file) in the class path and is responsible
+	 * for scanning resources from this location.
+	 */
+	static final class LocationInfo {
+		final File home;
+		private final ClassLoader classloader;
+
+		LocationInfo(File home, ClassLoader classloader) {
+			this.home = checkNotNull(home);
+			this.classloader = checkNotNull(classloader);
+		}
+
+		/** Returns the file this location is from. */
+		public final File file() {
+			return home;
+		}
+
+		/** Scans this location and returns all scanned resources. */
+		public ImmutableSet<ResourceInfo> scanResources() throws IOException {
+			return scanResources(new HashSet<File>());
+		}
+
+		/**
+		 * Scans this location and returns all scanned resources.
+		 *
+		 * <p>This file and jar files from "Class-Path" entry in the scanned manifest files will be
+		 * added to {@code scannedFiles}.
+		 *
+		 * <p>A file will be scanned at most once even if specified multiple times by one or multiple
+		 * jar files' "Class-Path" manifest entries. Particularly, if a jar file from the "Class-Path"
+		 * manifest entry is already in {@code scannedFiles}, either because it was scanned earlier, or
+		 * it was intentionally added to the set by the caller, it will not be scanned again.
+		 *
+		 * <p>Note that when you call {@code location.scanResources(scannedFiles)}, the location will
+		 * always be scanned even if {@code scannedFiles} already contains it.
+		 */
+		public ImmutableSet<ResourceInfo> scanResources(Set<File> scannedFiles) throws IOException {
+			ImmutableSet.Builder<ResourceInfo> builder = ImmutableSet.builder();
+			scannedFiles.add(home);
+			scan(home, scannedFiles, builder);
+			return builder.build();
+		}
+
+		private void scan(File file, Set<File> scannedUris, ImmutableSet.Builder<ResourceInfo> builder)
+			throws IOException {
+			try {
+				if (!file.exists()) {
+					return;
+				}
+			} catch (SecurityException e) {
+				logger.warning("Cannot access " + file + ": " + e);
+				// TODO(emcmanus): consider whether to log other failure cases too.
+				return;
+			}
+			if (file.isDirectory()) {
+				scanDirectory(file, builder);
+			} else {
+				scanJar(file, scannedUris, builder);
+			}
+		}
+
+		private void scanJar(
+			File file, Set<File> scannedUris, ImmutableSet.Builder<ResourceInfo> builder)
+			throws IOException {
+			JarFile jarFile;
+			try {
+				jarFile = new JarFile(file);
+			} catch (IOException e) {
+				// Not a jar file
+				return;
+			}
+			try {
+				for (File path : getClassPathFromManifest(file, jarFile.getManifest())) {
+					// We only scan each file once independent of the classloader that file might be
+					// associated with.
+					if (scannedUris.add(path.getCanonicalFile())) {
+						scan(path, scannedUris, builder);
+					}
+				}
+				scanJarFile(jarFile, builder);
+			} finally {
+				try {
+					jarFile.close();
+				} catch (IOException ignored) { // similar to try-with-resources, but don't fail scanning
+				}
+			}
+		}
+
+		private void scanJarFile(JarFile file, ImmutableSet.Builder<ResourceInfo> builder) {
+			Enumeration<JarEntry> entries = file.entries();
+			while (entries.hasMoreElements()) {
+				JarEntry entry = entries.nextElement();
+				if (entry.isDirectory() || entry.getName().equals(JarFile.MANIFEST_NAME)) {
+					continue;
+				}
+				builder.add(ResourceInfo.of(new File(file.getName()), entry.getName(), classloader));
+			}
+		}
+
+		private void scanDirectory(File directory, ImmutableSet.Builder<ResourceInfo> builder)
+			throws IOException {
+			Set<File> currentPath = new HashSet<>();
+			currentPath.add(directory.getCanonicalFile());
+			scanDirectory(directory, "", currentPath, builder);
+		}
+
+		/**
+		 * Recursively scan the given directory, adding resources for each file encountered. Symlinks
+		 * which have already been traversed in the current tree path will be skipped to eliminate
+		 * cycles; otherwise symlinks are traversed.
+		 *
+		 * @param directory the root of the directory to scan
+		 * @param packagePrefix resource path prefix inside {@code classloader} for any files found
+		 *     under {@code directory}
+		 * @param currentPath canonical files already visited in the current directory tree path, for
+		 *     cycle elimination
+		 */
+		private void scanDirectory(
+			File directory,
+			String packagePrefix,
+			Set<File> currentPath,
+			ImmutableSet.Builder<ResourceInfo> builder)
+			throws IOException {
+			File[] files = directory.listFiles();
+			if (files == null) {
+				logger.warning("Cannot read directory " + directory);
+				// IO error, just skip the directory
+				return;
+			}
+			for (File f : files) {
+				String name = f.getName();
+				if (f.isDirectory()) {
+					File deref = f.getCanonicalFile();
+					if (currentPath.add(deref)) {
+						scanDirectory(deref, packagePrefix + name + "/", currentPath, builder);
+						currentPath.remove(deref);
+					}
+				} else {
+					String resourceName = packagePrefix + name;
+					if (!resourceName.equals(JarFile.MANIFEST_NAME)) {
+						builder.add(ResourceInfo.of(f, resourceName, classloader));
+					}
+				}
+			}
+		}
+
+		@Override
+		public boolean equals(@CheckForNull Object obj) {
+			if (obj instanceof LocationInfo) {
+				LocationInfo that = (LocationInfo) obj;
+				return home.equals(that.home) && classloader.equals(that.classloader);
+			}
+			return false;
+		}
+
+		@Override
+		public int hashCode() {
+			return home.hashCode();
+		}
+
+		@Override
+		public String toString() {
+			return home.toString();
+		}
+	}
+
+	/**
+	 * Returns the class path URIs specified by the {@code Class-Path} manifest attribute, according
+	 * to <a
+	 * href="http://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html#Main_Attributes">JAR
+	 * File Specification</a>. If {@code manifest} is null, it means the jar file has no manifest, and
+	 * an empty set will be returned.
+	 */
+	@VisibleForTesting
+	static ImmutableSet<File> getClassPathFromManifest(
+		File jarFile, @CheckForNull Manifest manifest) {
+		if (manifest == null) {
+			return ImmutableSet.of();
+		}
+		ImmutableSet.Builder<File> builder = ImmutableSet.builder();
+		String classpathAttribute =
+			manifest.getMainAttributes().getValue(Attributes.Name.CLASS_PATH.toString());
+		if (classpathAttribute != null) {
+			for (String path : CLASS_PATH_ATTRIBUTE_SEPARATOR.split(classpathAttribute)) {
+				URL url;
+				try {
+					url = getClassPathEntry(jarFile, path);
+				} catch (MalformedURLException e) {
+					// Ignore bad entry
+					logger.warning("Invalid Class-Path entry: " + path);
+					continue;
+				}
+				if (url.getProtocol().equals("file")) {
+					builder.add(toFile(url));
+				}
+			}
+		}
+		return builder.build();
+	}
+
+	@VisibleForTesting
+	static ImmutableMap<File, ClassLoader> getClassPathEntries(ClassLoader classloader) {
+		LinkedHashMap<File, ClassLoader> entries = Maps.newLinkedHashMap();
+		// Search parent first, since it's the order ClassLoader#loadClass() uses.
+		ClassLoader parent = classloader.getParent();
+		if (parent != null) {
+			entries.putAll(getClassPathEntries(parent));
+		}
+		for (URL url : getClassLoaderUrls(classloader)) {
+			if (url.getProtocol().equals("file")) {
+				File file = toFile(url);
+				if (!entries.containsKey(file)) {
+					entries.put(file, classloader);
+				}
+			}
+		}
+		return ImmutableMap.copyOf(entries);
+	}
+
+	private static ImmutableList<URL> getClassLoaderUrls(ClassLoader classloader) {
+		if (classloader instanceof URLClassLoader) {
+			return ImmutableList.copyOf(((URLClassLoader) classloader).getURLs());
+		}
+		if (classloader.equals(ClassLoader.getSystemClassLoader())) {
+			return parseJavaClassPath();
+		}
+		return ImmutableList.of();
+	}
+
+	/**
+	 * Returns the URLs in the class path specified by the {@code java.class.path} {@linkplain
+	 * System#getProperty system property}.
+	 */
+	@VisibleForTesting // TODO(b/65488446): Make this a public API.
+	static ImmutableList<URL> parseJavaClassPath() {
+		ImmutableList.Builder<URL> urls = ImmutableList.builder();
+		for (String entry : Splitter.on(PATH_SEPARATOR.value()).split(JAVA_CLASS_PATH.value())) {
+			try {
+				try {
+					urls.add(new File(entry).toURI().toURL());
+				} catch (SecurityException e) { // File.toURI checks to see if the file is a directory
+					urls.add(new URL("file", null, new File(entry).getAbsolutePath()));
+				}
+			} catch (MalformedURLException e) {
+				logger.log(WARNING, "malformed classpath entry: " + entry, e);
+			}
+		}
+		return urls.build();
+	}
+
+	/**
+	 * Returns the absolute uri of the Class-Path entry value as specified in <a
+	 * href="http://docs.oracle.com/javase/8/docs/technotes/guides/jar/jar.html#Main_Attributes">JAR
+	 * File Specification</a>. Even though the specification only talks about relative urls, absolute
+	 * urls are actually supported too (for example, in Maven surefire plugin).
+	 */
+	@VisibleForTesting
+	static URL getClassPathEntry(File jarFile, String path) throws MalformedURLException {
+		return new URL(jarFile.toURI().toURL(), path);
+	}
+
+	@VisibleForTesting
+	static String getClassName(String filename) {
+		int classNameEnd = filename.length() - CLASS_FILE_NAME_EXTENSION.length();
+		return filename.substring(0, classNameEnd).replace('/', '.');
+	}
+
+	// TODO(benyu): Try java.nio.file.Paths#get() when Guava drops JDK 6 support.
+	@VisibleForTesting
+	static File toFile(URL url) {
+		checkArgument(url.getProtocol().equals("file"));
+		try {
+			return new File(url.toURI()); // Accepts escaped characters like %20.
+		} catch (URISyntaxException e) { // URL.toURI() doesn't escape chars.
+			return new File(url.getPath()); // Accepts non-escaped chars like space.
+		}
+	}
+}