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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.Attribute;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.visitor.ClassVisitor;

/**
 * This {@link ClassVisitor} shares strings in the class files that it visits.
 *
 * @author Eric Lafortune
 */
public class StringSharer implements ClassVisitor, ConstantVisitor, AttributeVisitor {
  // A fields acting as an argument for the visitor methods.
  private String name;
  private String type;

  // Implementations for ClassVisitor.

  @Override
  public void visitAnyClass(Clazz clazz) {
    throw new UnsupportedOperationException(
        this.getClass().getName() + " does not support " + clazz.getClass().getName());
  }

  @Override
  public void visitProgramClass(ProgramClass programClass) {
    // Replace name strings in the constant pool by shared strings.
    programClass.constantPoolEntriesAccept(this);

    // Replace attribute name strings in the constant pool by internalized
    // strings.
    programClass.attributesAccept(this);
  }

  @Override
  public void visitLibraryClass(LibraryClass libraryClass) {
    // Replace the super class name string by the shared name string.
    Clazz superClass = libraryClass.superClass;
    if (superClass != null) {
      libraryClass.superClassName = superClass.getName();
    }

    // Replace the interface name strings by the shared name strings.
    if (libraryClass.interfaceNames != null) {
      String[] interfaceNames = libraryClass.interfaceNames;
      Clazz[] interfaceClasses = libraryClass.interfaceClasses;

      for (int index = 0; index < interfaceNames.length; index++) {
        // Keep a reference to the interface class.
        Clazz interfaceClass = interfaceClasses[index];
        if (interfaceClass != null) {
          interfaceNames[index] = interfaceClass.getName();
        }
      }
    }
  }

  // Implementations for ConstantVisitor.

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

  public void visitStringConstant(Clazz clazz, StringConstant stringConstant) {
    Member referencedMember = stringConstant.referencedMember;
    if (referencedMember != null) {
      Clazz referencedClass = stringConstant.referencedClass;

      // Put the actual class member's name in the class pool.
      name = referencedMember.getName(referencedClass);
      clazz.constantPoolEntryAccept(stringConstant.u2stringIndex, this);
    }
  }

  public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant) {
    Field referencedField = fieldrefConstant.referencedField;
    if (referencedField != null) {
      Clazz referencedClass = fieldrefConstant.referencedClass;

      // Put the actual class field's name and type strings in the class
      // pool.
      name = referencedField.getName(referencedClass);
      type = referencedField.getDescriptor(referencedClass);
      clazz.constantPoolEntryAccept(fieldrefConstant.u2nameAndTypeIndex, this);
    }
  }

  public void visitAnyMethodrefConstant(Clazz clazz, AnyMethodrefConstant anyMethodrefConstant) {
    Method referencedMethod = anyMethodrefConstant.referencedMethod;
    if (referencedMethod != null) {
      Clazz referencedClass = anyMethodrefConstant.referencedClass;

      // Put the actual class method's name and type strings in the class
      // pool.
      name = referencedMethod.getName(referencedClass);
      type = referencedMethod.getDescriptor(referencedClass);
      clazz.constantPoolEntryAccept(anyMethodrefConstant.u2nameAndTypeIndex, this);
    }
  }

  public void visitNameAndTypeConstant(Clazz clazz, NameAndTypeConstant nameAndTypeConstant) {
    if (name != null) {
      // Put the actual class member's name and type strings in the class
      // pool.
      clazz.constantPoolEntryAccept(nameAndTypeConstant.u2nameIndex, this);
      name = type;
      clazz.constantPoolEntryAccept(nameAndTypeConstant.u2descriptorIndex, this);
    }
  }

  public void visitClassConstant(Clazz clazz, ClassConstant classConstant) {
    Clazz referencedClass = classConstant.referencedClass;
    if (referencedClass != null) {
      // Put the actual class's name string in the class pool.
      name = referencedClass.getName();
      clazz.constantPoolEntryAccept(classConstant.u2nameIndex, this);
    }
  }

  public void visitUtf8Constant(Clazz clazz, Utf8Constant utf8Constant) {
    // Do we have a new string to put into this constant?
    if (name != null) {
      // Replace the string, if it's actually the same.
      if (name.equals(utf8Constant.getString())) {
        utf8Constant.setString(name);
      }

      name = null;
    }
  }

  // Implementations for AttributeVisitor.

  public void visitAnyAttribute(Clazz clazz, Attribute attribute) {
    // Put the internalized attribute's name string in the class pool.
    name = attribute.getAttributeName(clazz).intern();
    clazz.constantPoolEntryAccept(attribute.u2attributeNameIndex, this);
  }
}