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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;

/* ====================================================================
 * 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 (https://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 java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import org.aspectj.apache.bcel.Constants;

/**
 * This class represents collection of local variables in a method. This attribute is contained in the Code attribute.
 *
 * @version $Id: LocalVariableTable.java,v 1.8 2009/09/15 19:40:12 aclement Exp $
 * @author M. Dahm
 * @see Code
 * @see LocalVariable Updates: Andy 14Feb06 - Made unpacking of the data lazy, depending on someone actually asking for it.
 */
public class LocalVariableTable extends Attribute {

	// if 'isInPackedState' then this data needs unpacking
	private boolean isInPackedState = false;
	private byte[] data;

	private int localVariableTableLength;
	private LocalVariable[] localVariableTable;

	/**
	 * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a physical
	 * copy.
	 */
	public LocalVariableTable(LocalVariableTable c) {
		this(c.getNameIndex(), c.getLength(), c.getLocalVariableTable(), c.getConstantPool());
	}

	/**
	 * @param name_index Index in constant pool to `LocalVariableTable'
	 * @param length Content length in bytes
	 * @param local_variable_table Table of local variables
	 * @param constant_pool Array of constants
	 */
	public LocalVariableTable(int name_index, int length, LocalVariable[] local_variable_table, ConstantPool constant_pool) {
		super(Constants.ATTR_LOCAL_VARIABLE_TABLE, name_index, length, constant_pool);
		setLocalVariableTable(local_variable_table);
	}

	/**
	 * Construct object from file stream.
	 *
	 * @param name_index Index in constant pool
	 * @param length Content length in bytes
	 * @param file Input stream
	 * @param constant_pool Array of constants
	 * @throws IOException
	 */
	LocalVariableTable(int name_index, int length, DataInputStream file, ConstantPool constant_pool) throws IOException {
		super(Constants.ATTR_LOCAL_VARIABLE_TABLE, name_index, length, constant_pool);
		data = new byte[length];
		file.readFully(data);
		isInPackedState = true;
		// assert(bytesRead==length)
	}

	/**
	 * Called by objects that are traversing the nodes of the tree implicitely defined by the contents of a Java class. I.e., the
	 * hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
	 *
	 * @param v Visitor object
	 */
	@Override
	public void accept(ClassVisitor v) {
		unpack();
		v.visitLocalVariableTable(this);
	}

	/**
	 * Dump local variable table attribute to file stream in binary format.
	 *
	 * @param file Output file stream
	 * @throws IOException
	 */
	@Override
	public final synchronized void dump(DataOutputStream file) throws IOException {
		super.dump(file);
		if (isInPackedState) {
			file.write(data);
		} else {
			file.writeShort(localVariableTableLength);
			for (int i = 0; i < localVariableTableLength; i++)
				localVariableTable[i].dump(file);
		}
	}

	/**
	 * @return Array of local variables of method.
	 */
	public final LocalVariable[] getLocalVariableTable() {
		unpack();
		return localVariableTable;
	}

	/**
	 * @return first matching variable using index
	 */
	public final LocalVariable getLocalVariable(int index) {
		unpack();
		for (int i = 0; i < localVariableTableLength; i++) {
			if (localVariableTable[i] != null && localVariableTable[i].getIndex() == index) {
				return localVariableTable[i];
			}
		}
		return null;
	}

	public synchronized final void setLocalVariableTable(LocalVariable[] local_variable_table) {
		data = null;
		isInPackedState = false;
		this.localVariableTable = local_variable_table;
		localVariableTableLength = (local_variable_table == null) ? 0 : local_variable_table.length;
	}

	/**
	 * @return String representation.
	 */
	@Override
	public final String toString() {
		StringBuilder buf = new StringBuilder("");
		unpack();
		for (int i = 0; i < localVariableTableLength; i++) {
			buf.append(localVariableTable[i].toString());

			if (i < localVariableTableLength - 1)
				buf.append('\n');
		}

		return buf.toString();
	}

	/**
	 * Returns copy of this attribute using same packed state. Used in unit tests.
	 */
	public synchronized LocalVariableTable copyFromPackedState() {
		if (!isInPackedState) throw new IllegalStateException("No in packed state");
		try {
			return new LocalVariableTable(nameIndex, length, new DataInputStream(new ByteArrayInputStream(data)), getConstantPool());
		} catch (IOException e) {
			throw new RuntimeException("Failed to unpack clone", e);
		}
	}

	/**
	 * @return deep copy of this attribute
	 */
	// public Attribute copy(ConstantPool constant_pool) {
	// unpack();
	// LocalVariableTable c = (LocalVariableTable) clone();
	//
	// c.localVariableTable = new LocalVariable[localVariableTableLength];
	// for (int i = 0; i < localVariableTableLength; i++)
	// c.localVariableTable[i] = localVariableTable[i].copy();
	//
	// c.cpool = constant_pool;
	// return c;
	// }
	public final int getTableLength() {
		unpack();
		return localVariableTableLength;
	}

	// ---
	// Unpacks the byte array into the table
	private synchronized void unpack() {
		if (!isInPackedState)
			return;
		try {
			ByteArrayInputStream bs = new ByteArrayInputStream(data);
			DataInputStream dis = new DataInputStream(bs);
			localVariableTableLength = (dis.readUnsignedShort());
			localVariableTable = new LocalVariable[localVariableTableLength];
			for (int i = 0; i < localVariableTableLength; i++)
				localVariableTable[i] = new LocalVariable(dis, cpool);
			dis.close();
			data = null; // throw it away now
		} catch (IOException e) {
			throw new RuntimeException("Unpacking of LocalVariableTable attribute failed", e);
		}
		isInPackedState = false;
	}
}