proguard.classfile.editor.MethodCopier Maven / Gradle / Ivy

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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) 2002-2023 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.editor;

import proguard.classfile.Clazz;
import proguard.classfile.Member;
import proguard.classfile.Method;
import proguard.classfile.ProgramClass;
import proguard.classfile.ProgramMethod;
import proguard.classfile.attribute.Attribute;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.attribute.ExtendedLineNumberInfo;
import proguard.classfile.attribute.LineNumberInfo;
import proguard.classfile.attribute.LineNumberTableAttribute;
import proguard.classfile.attribute.visitor.AllAttributeVisitor;
import proguard.classfile.attribute.visitor.AttributeNameFilter;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.visitor.ClassVisitor;
import proguard.classfile.visitor.MemberVisitor;
import proguard.classfile.visitor.MultiMemberVisitor;
import proguard.util.StringFunction;

/**
 * This {@link ClassVisitor} copies a method into a target class. It first checks if a method with
 * the same name and descriptor as the method to be copied already exists in the target class. If
 * that is indeed the case, this visitor is a no-op. This visitor optionally uses a name transformer
 * function to apply to the original method's name before copying. If no name transformer function
 * is provided, the original method's name is used, instead. If the method to be copied is indeed
 * copied into the target class, this visitor passes the resulting method to an extra member
 * visitor, if provided.
 */
public class MethodCopier implements ClassVisitor, MemberVisitor, AttributeVisitor {
  private final ProgramClass sourceClass;
  private final ProgramMethod sourceMethod;
  private final StringFunction nameTransformer;
  private final MemberVisitor extraMemberVisitor;

  public MethodCopier(ProgramClass sourceClass, ProgramMethod sourceMethod) {
    this(sourceClass, sourceMethod, null);
  }

  public MethodCopier(
      ProgramClass sourceClass, ProgramMethod sourceMethod, StringFunction nameTransformer) {
    this(sourceClass, sourceMethod, nameTransformer, null);
  }

  public MethodCopier(
      ProgramClass sourceClass,
      ProgramMethod sourceMethod,
      StringFunction nameTransformer,
      MemberVisitor extraMemberVisitor) {
    this.sourceClass = sourceClass;
    this.sourceMethod = sourceMethod;
    this.nameTransformer = nameTransformer;
    this.extraMemberVisitor = extraMemberVisitor;
  }

  // ClassVisitor

  @Override
  public void visitAnyClass(Clazz clazz) {}

  @Override
  public void visitProgramClass(ProgramClass programClass) {
    if (methodAlreadyExistsInClass(programClass)) {
      return;
    }

    MemberVisitor copiedMethodVisitor =
        extraMemberVisitor == null ? this : new MultiMemberVisitor(this, extraMemberVisitor);

    new MemberAdder(programClass, nameTransformer, copiedMethodVisitor)
        .visitProgramMethod(sourceClass, sourceMethod);
  }

  private boolean methodAlreadyExistsInClass(ProgramClass programClass) {
    String sourceMethodName = sourceMethod.getName(sourceClass);
    String sourceMethodDescriptor = sourceMethod.getDescriptor(sourceClass);

    String toCheckName =
        nameTransformer == null ? sourceMethodName : nameTransformer.transform(sourceMethodName);

    return programClass.findMethod(toCheckName, sourceMethodDescriptor) != null;
  }

  // MemberVisitor

  @Override
  public void visitAnyMember(Clazz clazz, Member member) {}

  @Override
  public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod) {
    programMethod.accept(
        programClass, new AllAttributeVisitor(new AttributeNameFilter(Attribute.CODE, this)));
  }

  // AttributeVisitor

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

  @Override
  public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) {
    // The source values for the copied method's line numbers should refer to the original method.
    LineNumberTableAttribute copiedMethodLineNumberTableAttribute =
        (LineNumberTableAttribute) codeAttribute.getAttribute(clazz, Attribute.LINE_NUMBER_TABLE);

    if (copiedMethodLineNumberTableAttribute == null
        || copiedMethodLineNumberTableAttribute.u2lineNumberTableLength == 0) {
      return;
    }

    sourceMethod.accept(
        sourceClass,
        new AllAttributeVisitor(
            new AttributeNameFilter(
                Attribute.CODE, new MyLineFixer(copiedMethodLineNumberTableAttribute))));
  }

  private static class MyLineFixer implements AttributeVisitor {
    private final LineNumberTableAttribute copiedMethodLineNumberTableAttribute;

    MyLineFixer(LineNumberTableAttribute copiedMethodLineNumberTableAttribute) {
      this.copiedMethodLineNumberTableAttribute = copiedMethodLineNumberTableAttribute;
    }

    public void visitCodeAttribute(
        Clazz sourceClass, Method sourceMethod, CodeAttribute sourceMethodCodeAttribute) {
      LineNumberTableAttribute sourceMethodLineNumberTableAttribute =
          (LineNumberTableAttribute)
              sourceMethodCodeAttribute.getAttribute(sourceClass, Attribute.LINE_NUMBER_TABLE);
      int lowestLineNumber =
          sourceMethodLineNumberTableAttribute == null
              ? 0
              : sourceMethodLineNumberTableAttribute.getLowestLineNumber();
      int highestLineNumber =
          sourceMethodLineNumberTableAttribute == null
              ? 0
              : sourceMethodLineNumberTableAttribute.getHighestLineNumber();

      String newSource =
          initializeLineNumberInfoSource(
              sourceClass, sourceMethod, lowestLineNumber, highestLineNumber);

      for (int i = 0; i < copiedMethodLineNumberTableAttribute.u2lineNumberTableLength; i++) {
        LineNumberInfo currentLineNumberInfo =
            copiedMethodLineNumberTableAttribute.lineNumberTable[i];
        ExtendedLineNumberInfo newLineNumberInfo =
            new ExtendedLineNumberInfo(
                currentLineNumberInfo.u2startPC, currentLineNumberInfo.u2lineNumber, newSource);
        copiedMethodLineNumberTableAttribute.lineNumberTable[i] = newLineNumberInfo;
      }
    }

    private String initializeLineNumberInfoSource(
        Clazz sourceClass, Method sourceMethod, int startLineNumber, int endLineNumber) {
      return sourceClass.getName()
          + "."
          + sourceMethod.getName(sourceClass)
          + sourceMethod.getDescriptor(sourceClass)
          + ":"
          + startLineNumber
          + ":"
          + endLineNumber;
    }
  }
}