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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.CodeAttribute;
import proguard.classfile.attribute.annotation.*;
import proguard.classfile.attribute.annotation.visitor.ElementValueVisitor;
import proguard.classfile.attribute.visitor.AllAttributeVisitor;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.*;
import proguard.classfile.visitor.MemberVisitor;

/**
 * This {@link ElementValueVisitor} initializes the field references of the {@link
 * EnumConstantElementValue} instances that it visits.
 *
 * @author Eric Lafortune
 */
public class EnumFieldReferenceInitializer
    implements ElementValueVisitor, InstructionVisitor, ConstantVisitor {
  // *
  private static final boolean DEBUG = false;
  /*/
  private static       boolean DEBUG = System.getProperty("efri") != null;
  //*/

  private MemberVisitor enumFieldFinder = new AllAttributeVisitor(new AllInstructionVisitor(this));

  // Fields acting as parameters and return values for the visitors.
  private String enumTypeName;
  private String enumConstantName;
  private boolean enumConstantNameFound;
  private Clazz referencedEnumClass;
  private Field referencedEnumField;

  // Implementations for ElementValueVisitor.

  public void visitAnyElementValue(Clazz clazz, Annotation annotation, ElementValue elementValue) {}

  public void visitEnumConstantElementValue(
      Clazz clazz, Annotation annotation, EnumConstantElementValue enumConstantElementValue) {
    if (enumConstantElementValue.referencedClasses != null
        && enumConstantElementValue.referencedClasses.length > 0) {
      referencedEnumClass = enumConstantElementValue.referencedClasses[0];
      if (referencedEnumClass != null) {
        // Try to find the enum field through the static enum
        // initialization code (at least for program classes).
        enumTypeName = enumConstantElementValue.getTypeName(clazz);
        enumConstantName = enumConstantElementValue.getConstantName(clazz);
        referencedEnumField = null;
        referencedEnumClass.methodAccept(
            ClassConstants.METHOD_NAME_CLINIT, ClassConstants.METHOD_TYPE_CLINIT, enumFieldFinder);

        // Otherwise try to find the enum field through its name.
        // The constant name could be different from the field name, if
        // the latter is already obfuscated.
        if (referencedEnumField == null) {
          referencedEnumField = referencedEnumClass.findField(enumConstantName, enumTypeName);
        }

        if (DEBUG) {
          System.out.println(
              "EnumFieldReferenceInitializer: ["
                  + referencedEnumClass.getName()
                  + "."
                  + enumConstantName
                  + "] -> "
                  + referencedEnumField);
        }

        enumConstantElementValue.referencedField = referencedEnumField;
      }
    }
  }

  // Implementations for InstructionVisitor.

  public void visitAnyInstruction(
      Clazz clazz,
      Method method,
      CodeAttribute codeAttribute,
      int offset,
      Instruction instruction) {}

  public void visitConstantInstruction(
      Clazz clazz,
      Method method,
      CodeAttribute codeAttribute,
      int offset,
      ConstantInstruction constantInstruction) {
    switch (constantInstruction.opcode) {
      case Instruction.OP_LDC:
      case Instruction.OP_LDC_W:
      case Instruction.OP_PUTSTATIC:
        clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
        break;
    }
  }

  // Implementations for ConstantVisitor.

  public void visitAnyConstant(Clazz clazz, Constant constant) {}

  public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {
    enumConstantNameFound = enumConstantName.equals(stringConstant.getString(clazz));
  }

  public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant) {
    if (enumConstantNameFound) {
      if (enumTypeName.equals(fieldrefConstant.getType(clazz))) {
        referencedEnumField = (Field) fieldrefConstant.referencedField;
      }

      enumConstantNameFound = false;
    }
  }
}