/*
* Copyright (C) 2025 The Android Open Source Project
*
* 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.android.dependencymapper;
import org.objectweb.asm.signature.SignatureReader;
import org.objectweb.asm.signature.SignatureVisitor;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.Opcodes;
import org.objectweb.asm.Type;
import org.objectweb.asm.TypePath;
import java.lang.annotation.RetentionPolicy;
import java.util.HashSet;
import java.util.Set;
/**
* An ASM based class visitor to analyze and club all dependencies of a java file.
* Most of the logic of this class is inspired from
* gradle incremental compilation
*/
public class ClassDependenciesVisitor extends ClassVisitor {
private final static int API = Opcodes.ASM9;
private final Set mClassTypes;
private final Set mConstantsDefined;
private final Set mInlinedUsages;
private String mSource;
private boolean isAnnotationType;
private boolean mIsDependencyToAll;
private final RetentionPolicyVisitor retentionPolicyVisitor;
private final ClassRelevancyFilter mClassFilter;
private ClassDependenciesVisitor(ClassReader reader, ClassRelevancyFilter filter) {
super(API);
this.mClassTypes = new HashSet<>();
this.mConstantsDefined = new HashSet<>();
this.mInlinedUsages = new HashSet<>();
this.retentionPolicyVisitor = new RetentionPolicyVisitor();
this.mClassFilter = filter;
collectRemainingClassDependencies(reader);
}
public static ClassDependencyData analyze(
String className, ClassReader reader, ClassRelevancyFilter filter) {
ClassDependenciesVisitor visitor = new ClassDependenciesVisitor(reader, filter);
reader.accept(visitor, ClassReader.SKIP_FRAMES);
// Sometimes a class may contain references to the same class, we remove such cases to
// prevent circular dependency.
visitor.getClassTypes().remove(className);
return new ClassDependencyData(Utils.buildPackagePrependedClassSource(
className, visitor.getSource()), className, visitor.getClassTypes(),
visitor.isDependencyToAll(), visitor.getConstantsDefined(),
visitor.getInlinedUsages());
}
@Override
public void visitSource(String source, String debug) {
mSource = source;
}
@Override
public void visit(int version, int access, String name, String signature, String superName,
String[] interfaces) {
isAnnotationType = isAnnotationType(interfaces);
maybeAddClassTypesFromSignature(signature, mClassTypes);
if (superName != null) {
// superName can be null if what we are analyzing is `java.lang.Object`
// which can happen when a custom Java SDK is on classpath (typically, android.jar)
Type type = Type.getObjectType(superName);
maybeAddClassType(mClassTypes, type);
}
for (String s : interfaces) {
Type interfaceType = Type.getObjectType(s);
maybeAddClassType(mClassTypes, interfaceType);
}
}
// performs a fast analysis of classes referenced in bytecode (method bodies)
// avoiding us to implement a costly visitor and potentially missing edge cases
private void collectRemainingClassDependencies(ClassReader reader) {
char[] charBuffer = new char[reader.getMaxStringLength()];
for (int i = 1; i < reader.getItemCount(); i++) {
int itemOffset = reader.getItem(i);
// see https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.4
if (itemOffset > 0 && reader.readByte(itemOffset - 1) == 7) {
// A CONSTANT_Class entry, read the class descriptor
String classDescriptor = reader.readUTF8(itemOffset, charBuffer);
Type type = Type.getObjectType(classDescriptor);
maybeAddClassType(mClassTypes, type);
}
}
}
private void maybeAddClassTypesFromSignature(String signature, Set types) {
if (signature != null) {
SignatureReader signatureReader = new SignatureReader(signature);
signatureReader.accept(new SignatureVisitor(API) {
@Override
public void visitClassType(String className) {
Type type = Type.getObjectType(className);
maybeAddClassType(types, type);
}
});
}
}
protected void maybeAddClassType(Set types, Type type) {
while (type.getSort() == Type.ARRAY) {
type = type.getElementType();
}
if (type.getSort() != Type.OBJECT) {
return;
}
//String name = Utils.classPackageToFilePath(type.getClassName());
String name = type.getClassName();
if (mClassFilter.test(name)) {
types.add(name);
}
}
public String getSource() {
return mSource;
}
public Set getClassTypes() {
return mClassTypes;
}
public Set getConstantsDefined() {
return mConstantsDefined;
}
public Set getInlinedUsages() {
return mInlinedUsages;
}
private boolean isAnnotationType(String[] interfaces) {
return interfaces.length == 1 && interfaces[0].equals("java/lang/annotation/Annotation");
}
@Override
public FieldVisitor visitField(
int access, String name, String desc, String signature, Object value) {
maybeAddClassTypesFromSignature(signature, mClassTypes);
maybeAddClassType(mClassTypes, Type.getType(desc));
if (isAccessibleConstant(access, value)) {
mConstantsDefined.add(value);
}
return new FieldVisitor(mClassTypes);
}
@Override
public MethodVisitor visitMethod(
int access, String name, String desc, String signature, String[] exceptions) {
maybeAddClassTypesFromSignature(signature, mClassTypes);
Type methodType = Type.getMethodType(desc);
maybeAddClassType(mClassTypes, methodType.getReturnType());
for (Type argType : methodType.getArgumentTypes()) {
maybeAddClassType(mClassTypes, argType);
}
return new MethodVisitor(mClassTypes);
}
@Override
public org.objectweb.asm.AnnotationVisitor visitAnnotation(String desc, boolean visible) {
if (isAnnotationType && "Ljava/lang/annotation/Retention;".equals(desc)) {
return retentionPolicyVisitor;
} else {
maybeAddClassType(mClassTypes, Type.getType(desc));
return new AnnotationVisitor(mClassTypes);
}
}
private static boolean isAccessible(int access) {
return (access & Opcodes.ACC_PRIVATE) == 0;
}
private static boolean isAccessibleConstant(int access, Object value) {
return isConstant(access) && isAccessible(access) && value != null;
}
private static boolean isConstant(int access) {
return (access & Opcodes.ACC_FINAL) != 0 && (access & Opcodes.ACC_STATIC) != 0;
}
public boolean isDependencyToAll() {
return mIsDependencyToAll;
}
private class FieldVisitor extends org.objectweb.asm.FieldVisitor {
private final Set types;
public FieldVisitor(Set types) {
super(API);
this.types = types;
}
@Override
public org.objectweb.asm.AnnotationVisitor visitAnnotation(
String descriptor, boolean visible) {
maybeAddClassType(types, Type.getType(descriptor));
return new AnnotationVisitor(types);
}
@Override
public org.objectweb.asm.AnnotationVisitor visitTypeAnnotation(int typeRef,
TypePath typePath, String descriptor, boolean visible) {
maybeAddClassType(types, Type.getType(descriptor));
return new AnnotationVisitor(types);
}
}
private class MethodVisitor extends org.objectweb.asm.MethodVisitor {
private final Set types;
protected MethodVisitor(Set types) {
super(API);
this.types = types;
}
@Override
public void visitLdcInsn(Object value) {
mInlinedUsages.add(value);
super.visitLdcInsn(value);
}
@Override
public void visitLocalVariable(
String name, String desc, String signature, Label start, Label end, int index) {
maybeAddClassTypesFromSignature(signature, mClassTypes);
maybeAddClassType(mClassTypes, Type.getType(desc));
super.visitLocalVariable(name, desc, signature, start, end, index);
}
@Override
public org.objectweb.asm.AnnotationVisitor visitAnnotation(
String descriptor, boolean visible) {
maybeAddClassType(types, Type.getType(descriptor));
return new AnnotationVisitor(types);
}
@Override
public org.objectweb.asm.AnnotationVisitor visitParameterAnnotation(
int parameter, String descriptor, boolean visible) {
maybeAddClassType(types, Type.getType(descriptor));
return new AnnotationVisitor(types);
}
@Override
public org.objectweb.asm.AnnotationVisitor visitTypeAnnotation(
int typeRef, TypePath typePath, String descriptor, boolean visible) {
maybeAddClassType(types, Type.getType(descriptor));
return new AnnotationVisitor(types);
}
}
private class RetentionPolicyVisitor extends org.objectweb.asm.AnnotationVisitor {
public RetentionPolicyVisitor() {
super(ClassDependenciesVisitor.API);
}
@Override
public void visitEnum(String name, String desc, String value) {
if ("Ljava/lang/annotation/RetentionPolicy;".equals(desc)) {
RetentionPolicy policy = RetentionPolicy.valueOf(value);
if (policy == RetentionPolicy.SOURCE) {
mIsDependencyToAll = true;
}
}
}
}
private class AnnotationVisitor extends org.objectweb.asm.AnnotationVisitor {
private final Set types;
public AnnotationVisitor(Set types) {
super(ClassDependenciesVisitor.API);
this.types = types;
}
@Override
public void visit(String name, Object value) {
if (value instanceof Type) {
maybeAddClassType(types, (Type) value);
}
}
@Override
public org.objectweb.asm.AnnotationVisitor visitArray(String name) {
return this;
}
@Override
public org.objectweb.asm.AnnotationVisitor visitAnnotation(String name, String descriptor) {
maybeAddClassType(types, Type.getType(descriptor));
return this;
}
}
}