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/*
* Copyright (C) 2020 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.inject.internal.aop;
import static com.google.inject.internal.aop.ClassDefining.hasPackageAccess;
import static java.lang.reflect.Modifier.FINAL;
import static java.lang.reflect.Modifier.PRIVATE;
import static java.lang.reflect.Modifier.PROTECTED;
import static java.lang.reflect.Modifier.PUBLIC;
import static java.lang.reflect.Modifier.STATIC;
import com.google.inject.TypeLiteral;
import com.google.inject.internal.BytecodeGen;
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
import java.util.function.BiFunction;
import java.util.function.Consumer;
import java.util.function.Function;
/**
* Entry-point for building enhanced classes and 'fast-class' invocation.
*
* @author [email protected] (Stuart McCulloch)
*/
public final class ClassBuilding {
private ClassBuilding() {}
private static final Method[] OVERRIDABLE_OBJECT_METHODS = getOverridableObjectMethods();
/** Minimum signature needed to disambiguate constructors from the same host class. */
public static String signature(Constructor constructor) {
return signature("", constructor.getParameterTypes());
}
/** Minimum signature needed to disambiguate methods from the same host class. */
public static String signature(Method method) {
return signature(method.getName(), method.getParameterTypes());
}
/** Appends a semicolon-separated list of parameter types to the given name. */
private static String signature(String name, Class[] parameterTypes) {
StringBuilder signature = new StringBuilder(name);
for (Class type : parameterTypes) {
signature.append(';').append(type.getName());
}
return signature.toString();
}
/** Returns true if the given member can be enhanced using bytecode. */
public static boolean canEnhance(Executable member) {
return canAccess(member, hasPackageAccess());
}
/** Builder of enhancers that provide method interception via bytecode generation. */
public static BytecodeGen.EnhancerBuilder buildEnhancerBuilder(Class hostClass) {
Map methodPartitions = new HashMap<>();
visitMethodHierarchy(
hostClass,
method -> {
// exclude static methods, but keep final methods for bridge analysis
if ((method.getModifiers() & STATIC) == 0) {
partitionMethod(method, methodPartitions);
}
});
Map enhanceableMethods = new TreeMap<>();
Map bridgeDelegates = new HashMap<>();
TypeLiteral hostType = TypeLiteral.get(hostClass);
for (Object partition : methodPartitions.values()) {
if (partition instanceof Method) {
// common case, partition is just one method; exclude if it turns out to be final
Method method = (Method) partition;
if ((method.getModifiers() & FINAL) == 0) {
enhanceableMethods.put(signature(method), method);
}
} else {
((MethodPartition) partition)
.collectEnhanceableMethods(
hostType,
method -> enhanceableMethods.put(signature(method), method),
bridgeDelegates);
}
}
return new EnhancerBuilderImpl(hostClass, enhanceableMethods.values(), bridgeDelegates);
}
/**
* Methods are partitioned by name and parameter count. This helps focus the search for bridge
* delegates that involve type-erasure of generic parameter types, since the parameter count will
* be the same for the bridge method and its delegate.
*/
private static void partitionMethod(Method method, Map partitions) {
String partitionKey = method.getName() + '/' + method.getParameterCount();
partitions.merge(partitionKey, method, ClassBuilding::mergeMethods);
}
/** Add the new method to an existing partition or create a new one. */
private static Object mergeMethods(Object existing, Object added) {
Method newMethod = (Method) added;
if (existing instanceof Method) {
return new MethodPartition((Method) existing, newMethod);
}
return ((MethodPartition) existing).addCandidate(newMethod);
}
/** Visit the method hierarchy for the host class. */
private static void visitMethodHierarchy(Class hostClass, Consumer visitor) {
// this is an iterative form of the following recursive search:
// 1. visit declared methods
// 2. recursively visit superclass
// 3. visit declared interfaces
// stack of interface declarations, from host class (bottom) to superclass (top)
Deque[]> interfaceStack = new ArrayDeque<>();
// only try to match package-private methods if the class-definer has package-access
String hostPackage = hasPackageAccess() ? packageName(hostClass.getName()) : null;
for (Class clazz = hostClass;
clazz != Object.class && clazz != null;
clazz = clazz.getSuperclass()) {
// optionally visit package-private methods matching the same package as the host
boolean samePackage = hostPackage != null && hostPackage.equals(packageName(clazz.getName()));
visitMembers(clazz.getDeclaredMethods(), samePackage, visitor);
pushInterfaces(interfaceStack, clazz.getInterfaces());
}
for (Method method : OVERRIDABLE_OBJECT_METHODS) {
visitor.accept(method);
}
// work our way back down the class hierarchy, merging and flattening interfaces into a list
List> interfaces = new ArrayList<>();
while (!interfaceStack.isEmpty()) {
for (Class intf : interfaceStack.pop()) {
if (mergeInterface(interfaces, intf)) {
pushInterfaces(interfaceStack, intf.getInterfaces());
}
}
}
// finally visit the methods declared in the flattened interface hierarchy
for (Class intf : interfaces) {
visitMembers(intf.getDeclaredMethods(), false, visitor);
}
}
/** Pushes the interface declaration onto the stack if it's not empty. */
private static void pushInterfaces(Deque[]> interfaceStack, Class[] interfaces) {
if (interfaces.length > 0) {
interfaceStack.push(interfaces);
}
}
/** Attempts to merge the interface with the current flattened hierarchy. */
private static boolean mergeInterface(List> interfaces, Class candidate) {
// work along the flattened hierarchy to find the appropriate merge point
for (int i = 0, len = interfaces.size(); i < len; i++) {
Class existingInterface = interfaces.get(i);
if (existingInterface == candidate) {
// already seen this interface, skip further processing
return false;
} else if (existingInterface.isAssignableFrom(candidate)) {
// extends existing interface, insert just before it in the flattened hierarchy
interfaces.add(i, candidate);
return true;
}
}
// unrelated or a superinterface, in both cases append to the flattened hierarchy
return interfaces.add(candidate);
}
/** Extract the package name from a class name. */
private static String packageName(String className) {
return className.substring(0, className.lastIndexOf('.') + 1);
}
/** Cache common overridable Object methods. */
private static Method[] getOverridableObjectMethods() {
List objectMethods = new ArrayList<>();
visitMembers(
Object.class.getDeclaredMethods(),
false, // no package-level access
method -> {
// skip methods that can't/shouldn't be overridden
if ((method.getModifiers() & (STATIC | FINAL)) == 0
&& !"finalize".equals(method.getName())) {
objectMethods.add(method);
}
});
return objectMethods.toArray(new Method[0]);
}
/** Returns true if the given member can be fast-invoked. */
public static boolean canFastInvoke(Executable member) {
int modifiers = member.getModifiers() & (PUBLIC | PRIVATE);
if (hasPackageAccess()) {
// can fast-invoke anything except private members
return modifiers != PRIVATE;
}
// can fast-invoke public members in public types whose parameters are all public
boolean visible = (modifiers == PUBLIC) && isPublic(member.getDeclaringClass());
if (visible) {
for (Class type : member.getParameterTypes()) {
if (!isPublic(type)) {
return false;
}
}
}
return visible;
}
private static boolean isPublic(Class clazz) {
return (clazz.getModifiers() & PUBLIC) != 0;
}
/** Builds a 'fast-class' invoker that uses bytecode generation in place of reflection. */
public static Function> buildFastClass(
Class hostClass) {
NavigableMap glueMap = new TreeMap<>();
visitFastConstructors(hostClass, ctor -> glueMap.put(signature(ctor), ctor));
visitFastMethods(hostClass, method -> glueMap.put(signature(method), method));
return new FastClass(hostClass).glue(glueMap);
}
/** Visit all constructors for the host class that can be fast-invoked. */
private static void visitFastConstructors(Class hostClass, Consumer> visitor) {
if (hasPackageAccess()) {
// can fast-invoke all non-private constructors
visitMembers(hostClass.getDeclaredConstructors(), true, visitor);
} else {
// can only fast-invoke public constructors
for (Constructor constructor : hostClass.getConstructors()) {
visitor.accept(constructor);
}
}
}
/** Visit all methods declared by the host class that can be fast-invoked. */
private static void visitFastMethods(Class hostClass, Consumer visitor) {
if (hasPackageAccess()) {
// can fast-invoke all non-private methods declared by the class
visitMembers(hostClass.getDeclaredMethods(), true, visitor);
} else {
// can only fast-invoke public methods
for (Method method : hostClass.getMethods()) {
// limit to those declared by this class; inherited methods have their own fast-class
if (hostClass == method.getDeclaringClass()) {
visitor.accept(method);
}
}
}
}
/** Visit all subclass accessible members in the given array. */
static void visitMembers(
T[] members, boolean samePackage, Consumer visitor) {
for (T member : members) {
if (canAccess(member, samePackage)) {
visitor.accept(member);
}
}
}
/** Can we access this member from a subclass which may be in the same package? */
private static boolean canAccess(Executable member, boolean samePackage) {
int modifiers = member.getModifiers();
// public and protected members are always ok, non-private also ok if in the same package
return (modifiers & (PUBLIC | PROTECTED)) != 0 || (samePackage && (modifiers & PRIVATE) == 0);
}
}
