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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) 2002-2022 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.analysis.cpa.defaults;

import java.util.Stack;

/**
 * This {@link StackAbstractState} represents a stack of {@link LatticeAbstractState}s with the
 * semilattice operators lifted to the stack.
 *
 * @author Dmitry Ivanov
 */
public class StackAbstractState>
    extends Stack
    implements LatticeAbstractState> {

  // implementations for LatticeAbstractState

  @Override
  public StackAbstractState join(StackAbstractState abstractState) {
    if (this == abstractState) {
      return this;
    }
    StackAbstractState joinResult = new StackAbstractState<>();
    StackAbstractState shorterState;
    StackAbstractState longerState;
    if (size() > abstractState.size()) {
      shorterState = abstractState;
      longerState = this;
    } else {
      shorterState = this;
      longerState = abstractState;
    }
    joinResult.addAll(longerState);
    for (int shortIndex = 0; shortIndex < shorterState.size(); ++shortIndex) {
      int longIndex = shortIndex + longerState.size() - shorterState.size();
      joinResult.set(longIndex, shorterState.get(shortIndex).join(longerState.get(longIndex)));
    }
    if (longerState.equals(joinResult)) {
      return longerState;
    }
    return joinResult;
  }

  @Override
  public boolean isLessOrEqual(StackAbstractState abstractState) {
    int sizeDifference = abstractState.size() - size();
    if (sizeDifference < 0) {
      return false;
    }
    for (int i = 0; i < size(); i++) {
      if (!get(i).isLessOrEqual(abstractState.get(i + sizeDifference))) {
        return false;
      }
    }
    return true;
  }

  @Override
  public StackAbstractState copy() {
    StackAbstractState copy = new StackAbstractState<>();
    copy.addAll(this);
    return copy;
  }

  /**
   * Removes the top of the stack and returns it. If the stack is empty, it returns the {@code
   * defaultState}.
   */
  public AbstractSpaceT popOrDefault(AbstractSpaceT defaultState) {
    return isEmpty() ? defaultState : pop();
  }

  /**
   * Returns the {@code index}th element from the top of the stack. If the stack does not have
   * enough elements, it throws an exception.
   */
  public AbstractSpaceT peek(int index) {
    int elementIndex = size() - 1 - index;
    if (elementIndex < 0) {
      throw new IllegalArgumentException("Operand stack index is out of bound (" + index + ")");
    } else {
      return get(elementIndex);
    }
  }

  /**
   * Returns the {@code index}th element from the top of the stack. If the stack does not have
   * enough elements, it returns the {@code defaultState}.
   */
  public AbstractSpaceT peekOrDefault(int index, AbstractSpaceT defaultState) {
    int elementIndex = size() - 1 - index;
    return elementIndex < 0 ? defaultState : get(elementIndex);
  }
}