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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.

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package org.aspectj.apache.bcel.classfile;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * .
 */

import  org.aspectj.apache.bcel.Constants;

/**
 * This class represents the type of a local variable or item on stack
 * used in the StackMap entries.
 *
 * @version $Id: StackMapType.java,v 1.3 2008/05/28 23:53:02 aclement Exp $
 * @author  M. Dahm
 * @see     StackMapEntry
 * @see     StackMap
 * @see     Constants
 */
public final class StackMapType implements Cloneable {
  private byte         type;
  private int          index = -1; // Index to CONSTANT_Class or offset
  private ConstantPool constant_pool;

  /**
   * Construct object from file stream.
   * @param file Input stream
   * @throws IOException
   */
  StackMapType(DataInputStream file, ConstantPool constant_pool) throws IOException
  {
    this(file.readByte(), -1, constant_pool);

    if(hasIndex())
      setIndex(file.readShort());

    setConstantPool(constant_pool);
  }

  /**
   * @param type type tag as defined in the Constants interface
   * @param index index to constant pool, or byte code offset
   */
  public StackMapType(byte type, int index, ConstantPool constant_pool) {
    setType(type);
    setIndex(index);
    setConstantPool(constant_pool);
  }

  public void setType(byte t) {
    if((t < Constants.ITEM_Bogus) || (t > Constants.ITEM_NewObject))
      throw new RuntimeException("Illegal type for StackMapType: " + t);
    type = t;
  }

  public byte getType()       { return type; }
  public void setIndex(int t) { index = t; }

  /** @return index to constant pool if type == ITEM_Object, or offset
   * in byte code, if type == ITEM_NewObject, and -1 otherwise
   */
  public int  getIndex()      { return index; }

  /**
   * Dump type entries to file.
   *
   * @param file Output file stream
   * @throws IOException
   */
  public final void dump(DataOutputStream file) throws IOException
  {
    file.writeByte(type);
    if(hasIndex())
      file.writeShort(getIndex());
  }

  /** @return true, if type is either ITEM_Object or ITEM_NewObject
   */
  public final boolean hasIndex() {
    return ((type == Constants.ITEM_Object) ||
	    (type == Constants.ITEM_NewObject));
  }

  private String printIndex() {
    if(type == Constants.ITEM_Object)
      return ", class=" + constant_pool.constantToString(index, Constants.CONSTANT_Class);
    else if(type == Constants.ITEM_NewObject)
      return ", offset=" + index;
    else
      return "";
  }

  /**
   * @return String representation
   */
  public final String toString() {
    return "(type=" + Constants.ITEM_NAMES[type] + printIndex() + ")";
  }

  /**
   * @return deep copy of this object
   */
  public StackMapType copy() {
    try {
      return (StackMapType)clone();
    } catch(CloneNotSupportedException e) {}

    return null;
  }

  /**
   * @return Constant pool used by this object.
   */
  public final ConstantPool getConstantPool() { return constant_pool; }

  /**
   * @param constant_pool Constant pool to be used for this object.
   */
  public final void setConstantPool(ConstantPool constant_pool) {
    this.constant_pool = constant_pool;
  }
}