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ProGuardCORE is a free library to read, analyze, modify, and write Java class files.

There is a newer version: 9.1.6

/*
 * ProGuardCORE -- library to process Java bytecode.
 *
 * Copyright (c) 2002-2020 Guardsquare NV
 *
 * 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 proguard.classfile.util;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.visitor.*;

/**
 * This utility class can find the nest host class names of given classes.
 *
 * @author Eric Lafortune
 */
public class NestHostFinder implements ClassVisitor, AttributeVisitor {
  private String nestHostClassName;

  /** Returns whether the two given classes are in the same nest. */
  public boolean inSameNest(Clazz class1, Clazz class2) {
    // Are the classes the same?
    if (class1.equals(class2)) {
      return true;
    }

    // Do the classes have the same nest host?
    String nestHostClassName1 = findNestHostClassName(class1);
    String nestHostClassName2 = findNestHostClassName(class2);

    return nestHostClassName1.equals(nestHostClassName2);
  }

  /**
   * Returns the class name of the nest host of the given class. This may be the class itself, if
   * the class doesn't have a nest host attribute (including for class versions below Java 11 and
   * for library classes).
   */
  public String findNestHostClassName(Clazz clazz) {
    // The default is the name of the class itself.
    nestHostClassName = clazz.getName();

    // Look for an explicit attribute.
    clazz.accept(this);

    // Return the found name.
    return nestHostClassName;
  }

  // Implementations for ClassVisitor.

  @Override
  public void visitAnyClass(Clazz clazz) {}

  @Override
  public void visitProgramClass(ProgramClass programClass) {
    // Only program classes store their versions and attributes.
    // The nest host attribute only exists since Java 10.
    if (programClass.u4version >= VersionConstants.CLASS_VERSION_10) {
      programClass.attributesAccept(this);
    }
  }

  // Implementations for AttributeVisitor.

  public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

  public void visitNestHostAttribute(Clazz clazz, NestHostAttribute nestHostAttribute) {
    // Remember the class name of the nest host.
    nestHostClassName = clazz.getClassName(nestHostAttribute.u2hostClassIndex);
  }
}