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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.generic;

/* ====================================================================
 * 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 java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.aspectj.apache.bcel.Constants;
import org.aspectj.apache.bcel.classfile.Constant;
import org.aspectj.apache.bcel.classfile.ConstantPool;
import org.aspectj.apache.bcel.util.ByteSequence;

/**
 * This class is a container for a list of Instruction objects. Instructions can be appended,
 * inserted, moved, deleted, etc.. Instructions are being wrapped into InstructionHandles
 * objects that are returned upon append/insert operations. They give the user (read only) access to the list structure, such that
 * it can be traversed and manipulated in a controlled way.
 *
 * A list is finally dumped to a byte code array with getByteCode.
 *
 * @version $Id: InstructionList.java,v 1.12 2011/09/02 22:33:04 aclement Exp $
 * @author M. Dahm
 * @author Abraham Nevado
 * @see Instruction
 * @see InstructionHandle
 * @see BranchHandle
 */
public class InstructionList implements Serializable {
	private InstructionHandle start = null, end = null;
	private int length = 0;
	private int[] positions; // byte code offsets corresponding to instructions

	public InstructionList() {
	}

	public InstructionList(Instruction i) {
		append(i);
	}

	public boolean isEmpty() {
		return start == null;
	} // && end == null

	public static InstructionHandle findHandle(InstructionHandle[] ihs, int[] pos, int count, int target) {
		return findHandle(ihs, pos, count, target, false);
	}

	/**
	 * Find the target instruction (handle) that corresponds to the given target position (byte code offset).
	 *
	 * @param ihs array of instruction handles, i.e. il.getInstructionHandles()
	 * @param pos array of positions corresponding to ihs, i.e. il.getInstructionPositions()
	 * @param count length of arrays
	 * @param target target position to search for
	 * @return target position's instruction handle if available
	 */
	public static InstructionHandle findHandle(InstructionHandle[] ihs, int[] pos, int count, int target,
			boolean returnClosestIfNoExactMatch) {
		int l = 0, r = count - 1;
		// Do a binary search since the pos array is ordered
		int i, j;
		do {
			i = (l + r) / 2;
			j = pos[i];
			if (j == target) {
				return ihs[i]; // found it
			} else if (target < j) {
				r = i - 1; // else constrain search area
			} else {
				l = i + 1; // target > j
			}
		} while (l <= r);

		if (returnClosestIfNoExactMatch) {
			i = (l + r) / 2;
			if (i < 0) {
				i = 0;
			}
			return ihs[i];
		}
		return null;
	}

	/**
	 * Get instruction handle for instruction at byte code position pos. This only works properly, if the list is freshly
	 * initialized from a byte array or setPositions() has been called before this method.
	 *
	 * @param pos byte code position to search for
	 * @return target position's instruction handle if available
	 */
	public InstructionHandle findHandle(int pos) {
		InstructionHandle[] ihs = getInstructionHandles();
		return findHandle(ihs, positions, length, pos);
	}

	public InstructionHandle[] getInstructionsAsArray() {
		return getInstructionHandles();
	}

	public InstructionHandle findHandle(int pos, InstructionHandle[] instructionArray) {
		return findHandle(instructionArray, positions, length, pos);
	}

	public InstructionHandle findHandle(int pos, InstructionHandle[] instructionArray, boolean useClosestApproximationIfNoExactFound) {
		return findHandle(instructionArray, positions, length, pos, useClosestApproximationIfNoExactFound);
	}

	/**
	 * Initialize instruction list from byte array.
	 *
	 * @param code byte array containing the instructions
	 */
	public InstructionList(byte[] code) {
		ByteSequence bytes = new ByteSequence(code);
		InstructionHandle[] ihs = new InstructionHandle[code.length];
		int[] pos = new int[code.length]; // Can't be more than that
		int count = 0; // Contains actual length

		/*
		 * Pass 1: Create an object for each byte code and append them to the list.
		 */
		try {
			while (bytes.available() > 0) {
				// Remember byte offset and associate it with the instruction
				int off = bytes.getIndex();
				pos[count] = off;

				/*
				 * Read one instruction from the byte stream, the byte position is set accordingly.
				 */
				Instruction i = Instruction.readInstruction(bytes);
				InstructionHandle ih;
				if (i instanceof InstructionBranch) {
					ih = append((InstructionBranch) i);
				} else {
					ih = append(i);
				}

				ih.setPosition(off);
				ihs[count] = ih;

				count++;
			}
		} catch (IOException e) {
			throw new ClassGenException(e.toString());
		}

		positions = new int[count]; // Trim to proper size
		System.arraycopy(pos, 0, positions, 0, count);

		/*
		 * Pass 2: Look for BranchInstruction and update their targets, i.e., convert offsets to instruction handles.
		 */
		// OPTIMIZE better way of doing this? keep little map from earlier from pos -> instruction handle?
		for (int i = 0; i < count; i++) {
			if (ihs[i] instanceof BranchHandle) {
				InstructionBranch bi = (InstructionBranch) ihs[i].instruction;
				int target = bi.positionOfThisInstruction + bi.getIndex(); /*
																			 * Byte code position: relative -> absolute.
																			 */
				// Search for target position
				InstructionHandle ih = findHandle(ihs, pos, count, target);

				if (ih == null) {
					throw new ClassGenException("Couldn't find target for branch: " + bi);
				}

				bi.setTarget(ih); // Update target

				// If it is a Select instruction, update all branch targets
				if (bi instanceof InstructionSelect) { // Either LOOKUPSWITCH or TABLESWITCH
					InstructionSelect s = (InstructionSelect) bi;
					int[] indices = s.getIndices();

					for (int j = 0; j < indices.length; j++) {
						target = bi.positionOfThisInstruction + indices[j];
						ih = findHandle(ihs, pos, count, target);

						if (ih == null) {
							throw new ClassGenException("Couldn't find target for switch: " + bi);
						}

						s.setTarget(j, ih); // Update target
					}
				}
			}
		}
	}

	/**
	 * Append another list after instruction (handle) ih contained in this list. Consumes argument list, i.e., it becomes empty.
	 *
	 * @param appendTo where to append the instruction list
	 * @param appendee Instruction list to append to this one
	 * @return instruction handle pointing to the first appended instruction
	 */
	public InstructionHandle append(InstructionHandle appendTo, InstructionList appendee) {
		assert appendee != null;

		if (appendee.isEmpty()) {
			return appendTo;
		}

		InstructionHandle next = appendTo.next;
		InstructionHandle ret = appendee.start;

		appendTo.next = appendee.start;
		appendee.start.prev = appendTo;

		appendee.end.next = next;

		if (next != null) {
			next.prev = appendee.end;
		} else {
			end = appendee.end; // Update end ...
		}

		length += appendee.length; // Update length

		appendee.clear();

		return ret;
	}

	/**
	 * Append another list after instruction i contained in this list. Consumes argument list, i.e., it becomes empty.
	 *
	 * @param i where to append the instruction list
	 * @param il Instruction list to append to this one
	 * @return instruction handle pointing to the first appended instruction
	 */
	public InstructionHandle append(Instruction i, InstructionList il) {
		InstructionHandle ih;

		if ((ih = findInstruction2(i)) == null) {
			throw new ClassGenException("Instruction " + i + " is not contained in this list.");
		}

		return append(ih, il);
	}

	/**
	 * Append another list to this one. Consumes argument list, i.e., it becomes empty.
	 *
	 * @param il list to append to end of this list
	 * @return instruction handle of the first appended instruction
	 */
	public InstructionHandle append(InstructionList il) {
		assert il != null;

		if (il.isEmpty()) {
			return null;
		}

		if (isEmpty()) {
			start = il.start;
			end = il.end;
			length = il.length;

			il.clear();

			return start;
		} else {
			return append(end, il); // was end.instruction
		}
	}

	/**
	 * Append an instruction to the end of this list.
	 *
	 * @param ih instruction to append
	 */
	private void append(InstructionHandle ih) {
		if (isEmpty()) {
			start = end = ih;
			ih.next = ih.prev = null;
		} else {
			end.next = ih;
			ih.prev = end;
			ih.next = null;
			end = ih;
		}

		length++; // Update length
	}

	/**
	 * Append an instruction to the end of this list.
	 *
	 * @param i instruction to append
	 * @return instruction handle of the appended instruction
	 */
	public InstructionHandle append(Instruction i) {
		InstructionHandle ih = InstructionHandle.getInstructionHandle(i);
		append(ih);

		return ih;
	}

	public InstructionHandle appendDUP() {
		InstructionHandle ih = InstructionHandle.getInstructionHandle(InstructionConstants.DUP);
		append(ih);
		return ih;
	}

	public InstructionHandle appendNOP() {
		InstructionHandle ih = InstructionHandle.getInstructionHandle(InstructionConstants.NOP);
		append(ih);
		return ih;
	}

	public InstructionHandle appendPOP() {
		InstructionHandle ih = InstructionHandle.getInstructionHandle(InstructionConstants.POP);
		append(ih);
		return ih;
	}

	/**
	 * Append a branch instruction to the end of this list.
	 *
	 * @param i branch instruction to append
	 * @return branch instruction handle of the appended instruction
	 */
	public BranchHandle append(InstructionBranch i) {
		BranchHandle ih = BranchHandle.getBranchHandle(i);
		append(ih);

		return ih;
	}

	/**
	 * Append a single instruction j after another instruction i, which must be in this list of course!
	 *
	 * @param i Instruction in list
	 * @param j Instruction to append after i in list
	 * @return instruction handle of the first appended instruction
	 */
	public InstructionHandle append(Instruction i, Instruction j) {
		return append(i, new InstructionList(j));
	}

	/**
	 * Append an instruction after instruction (handle) ih contained in this list.
	 *
	 * @param ih where to append the instruction list
	 * @param i Instruction to append
	 * @return instruction handle pointing to the first appended instruction
	 */
	public InstructionHandle append(InstructionHandle ih, Instruction i) {
		return append(ih, new InstructionList(i));
	}

	/**
	 * Append an instruction after instruction (handle) ih contained in this list.
	 *
	 * @param ih where to append the instruction list
	 * @param i Instruction to append
	 * @return instruction handle pointing to the first appended instruction
	 */
	public BranchHandle append(InstructionHandle ih, InstructionBranch i) {
		BranchHandle bh = BranchHandle.getBranchHandle(i);
		InstructionList il = new InstructionList();
		il.append(bh);

		append(ih, il);

		return bh;
	}

	/**
	 * Insert another list before Instruction handle ih contained in this list. Consumes argument list, i.e., it becomes empty.
	 *
	 * @param i where to append the instruction list
	 * @param il Instruction list to insert
	 * @return instruction handle of the first inserted instruction
	 */
	public InstructionHandle insert(InstructionHandle ih, InstructionList il) {
		if (il == null) {
			throw new ClassGenException("Inserting null InstructionList");
		}

		if (il.isEmpty()) {
			return ih;
		}

		InstructionHandle prev = ih.prev, ret = il.start;

		ih.prev = il.end;
		il.end.next = ih;

		il.start.prev = prev;

		if (prev != null) {
			prev.next = il.start;
		} else {
			start = il.start; // Update start ...
		}

		length += il.length; // Update length

		il.clear();

		return ret;
	}

	/**
	 * Insert another list.
	 *
	 * @param il list to insert before start of this list
	 * @return instruction handle of the first inserted instruction
	 */
	public InstructionHandle insert(InstructionList il) {
		if (isEmpty()) {
			append(il); // Code is identical for this case
			return start;
		} else {
			return insert(start, il);
		}
	}

	/**
	 * Insert an instruction at start of this list.
	 *
	 * @param ih instruction to insert
	 */
	private void insert(InstructionHandle ih) {
		if (isEmpty()) {
			start = end = ih;
			ih.next = ih.prev = null;
		} else {
			start.prev = ih;
			ih.next = start;
			ih.prev = null;
			start = ih;
		}

		length++;
	}

	/**
	 * Insert another list before Instruction i contained in this list. Consumes argument list, i.e., it becomes empty.
	 *
	 * @param i where to append the instruction list
	 * @param il Instruction list to insert
	 * @return instruction handle pointing to the first inserted instruction, i.e., il.getStart()
	 */
	public InstructionHandle insert(Instruction i, InstructionList il) {
		InstructionHandle ih;

		if ((ih = findInstruction1(i)) == null) {
			throw new ClassGenException("Instruction " + i + " is not contained in this list.");
		}

		return insert(ih, il);
	}

	/**
	 * Insert an instruction at start of this list.
	 *
	 * @param i instruction to insert
	 * @return instruction handle of the inserted instruction
	 */
	public InstructionHandle insert(Instruction i) {
		InstructionHandle ih = InstructionHandle.getInstructionHandle(i);
		insert(ih);

		return ih;
	}

	/**
	 * Insert a branch instruction at start of this list.
	 *
	 * @param i branch instruction to insert
	 * @return branch instruction handle of the appended instruction
	 */
	public BranchHandle insert(InstructionBranch i) {
		BranchHandle ih = BranchHandle.getBranchHandle(i);
		insert(ih);
		return ih;
	}

	/**
	 * Insert a single instruction j before another instruction i, which must be in this list of course!
	 *
	 * @param i Instruction in list
	 * @param j Instruction to insert before i in list
	 * @return instruction handle of the first inserted instruction
	 */
	public InstructionHandle insert(Instruction i, Instruction j) {
		return insert(i, new InstructionList(j));
	}

	/**
	 * Insert an instruction before instruction (handle) ih contained in this list.
	 *
	 * @param ih where to insert to the instruction list
	 * @param i Instruction to insert
	 * @return instruction handle of the first inserted instruction
	 */
	public InstructionHandle insert(InstructionHandle ih, Instruction i) {
		return insert(ih, new InstructionList(i));
	}

	/**
	 * Insert an instruction before instruction (handle) ih contained in this list.
	 *
	 * @param ih where to insert to the instruction list
	 * @param i Instruction to insert
	 * @return instruction handle of the first inserted instruction
	 */
	public BranchHandle insert(InstructionHandle ih, InstructionBranch i) {
		BranchHandle bh = BranchHandle.getBranchHandle(i);
		InstructionList il = new InstructionList();
		il.append(bh);

		insert(ih, il);

		return bh;
	}

	/**
	 * Take all instructions (handles) from "start" to "end" and append them after the new location "target". Of course, "end" must
	 * be after "start" and target must not be located withing this range. If you want to move something to the start of the list
	 * use null as value for target.

	 * Any instruction targeters pointing to handles within the block, keep their targets.
	 *
	 * @param start of moved block
	 * @param end of moved block
	 * @param target of moved block
	 */
	public void move(InstructionHandle start, InstructionHandle end, InstructionHandle target) {
		// Step 1: Check constraints

		if (start == null || end == null) {
			throw new ClassGenException("Invalid null handle: From " + start + " to " + end);
		}

		if (target == start || target == end) {
			throw new ClassGenException("Invalid range: From " + start + " to " + end + " contains target " + target);
		}

		for (InstructionHandle ih = start; ih != end.next; ih = ih.next) {
			if (ih == null) {
				throw new ClassGenException("Invalid range: From " + start + " to " + end);
			} else if (ih == target) {
				throw new ClassGenException("Invalid range: From " + start + " to " + end + " contains target " + target);
			}
		}

		// Step 2: Temporarily remove the given instructions from the list

		InstructionHandle prev = start.prev, next = end.next;

		if (prev != null) {
			prev.next = next;
		} else {
			this.start = next;
		}

		if (next != null) {
			next.prev = prev;
		} else {
			this.end = prev;
		}

		start.prev = end.next = null;

		// Step 3: append after target

		if (target == null) { // append to start of list
			end.next = this.start;
			this.start = start;
		} else {
			next = target.next;

			target.next = start;
			start.prev = target;
			end.next = next;

			if (next != null) {
				next.prev = end;
			}
		}
	}

	/**
	 * Move a single instruction (handle) to a new location.
	 *
	 * @param ih moved instruction
	 * @param target new location of moved instruction
	 */
	public void move(InstructionHandle ih, InstructionHandle target) {
		move(ih, ih, target);
	}

	/**
	 * Remove from instruction 'prev' to instruction 'next' both contained in this list.
	 *
	 * If careAboutLostTargeters is true then this method will throw a TargetLostException when one of the removed instruction
	 * handles is still being targeted.
	 *
	 * @param prev where to start deleting (predecessor, exclusive)
	 * @param next where to end deleting (successor, exclusive)
	 */
	private void remove(InstructionHandle prev, InstructionHandle next, boolean careAboutLostTargeters) throws TargetLostException {
		InstructionHandle first, last; // First and last deleted instruction

		if (prev == null && next == null) { // singleton list
			first = last = start;
			start = end = null;
		} else {
			if (prev == null) { // At start of list
				first = start;
				start = next;
			} else {
				first = prev.next;
				prev.next = next;
			}
			if (next == null) { // At end of list
				last = end;
				end = prev;
			} else {
				last = next.prev;
				next.prev = prev;
			}
		}

		first.prev = null; // Completely separated from rest of list
		last.next = null;

		if (!careAboutLostTargeters) {
			return;
		}

		List target_vec = new ArrayList<>();

		for (InstructionHandle ih = first; ih != null; ih = ih.next) {
			ih.getInstruction().dispose(); // e.g. BranchInstructions release their targets
		}

		StringBuilder buf = new StringBuilder("{ ");
		for (InstructionHandle ih = first; ih != null; ih = next) {
			next = ih.next;
			length--;

			Set targeters = ih.getTargeters();
			boolean isOK = false;
			for (InstructionTargeter instructionTargeter : targeters) {
				if (instructionTargeter.getClass().getName().endsWith("ShadowRange")
						|| instructionTargeter.getClass().getName().endsWith("ExceptionRange")
						|| instructionTargeter.getClass().getName().endsWith("LineNumberTag")) {
					isOK = true;
				} else {
					System.out.println(instructionTargeter.getClass());
				}
			}
			if (!isOK) {
				target_vec.add(ih);
				buf.append(ih.toString(true) + " ");
				ih.next = ih.prev = null;
			} else {
				ih.dispose();
			}

			// if (ih.hasTargeters()) { // Still got targeters?
			// InstructionTargeter[] targeters = ih.getTargeters();
			// boolean isOK = false;
			// for (int i = 0; i < targeters.length; i++) {
			// InstructionTargeter instructionTargeter = targeters[i];
			// if (instructionTargeter.getClass().getName().endsWith("ShadowRange")
			// || instructionTargeter.getClass().getName().endsWith("ExceptionRange")
			// || instructionTargeter.getClass().getName().endsWith("LineNumberTag")) {
			// isOK = true;
			// } else {
			// System.out.println(instructionTargeter.getClass());
			// }
			// }
			// if (!isOK) {
			// target_vec.add(ih);
			// buf.append(ih.toString(true) + " ");
			// ih.next = ih.prev = null;
			// } else {
			// ih.dispose();
			// }
			// } else {
			// ih.dispose();
			// }
		}

		buf.append("}");

		if (!target_vec.isEmpty()) {
			InstructionHandle[] targeted = new InstructionHandle[target_vec.size()];
			target_vec.toArray(targeted);
			throw new TargetLostException(targeted, buf.toString());
		}
	}

	/**
	 * Remove instruction from this list. The corresponding Instruction handles must not be reused!
	 *
	 * @param ih instruction (handle) to remove
	 */
	public void delete(InstructionHandle ih) throws TargetLostException {
		remove(ih.prev, ih.next, false);
	}

	/**
	 * Remove instruction from this list. The corresponding Instruction handles must not be reused!
	 *
	 * @param i instruction to remove
	 */
	// public void delete(Instruction i) throws TargetLostException {
	// InstructionHandle ih;
	//
	// if((ih = findInstruction1(i)) == null)
	// throw new ClassGenException("Instruction " + i +
	// " is not contained in this list.");
	// delete(ih);
	// }
	/**
	 * Remove instructions from instruction `from' to instruction `to' contained in this list. The user must ensure that `from' is
	 * an instruction before `to', or risk havoc. The corresponding Instruction handles must not be reused!
	 *
	 * @param from where to start deleting (inclusive)
	 * @param to where to end deleting (inclusive)
	 */
	public void delete(InstructionHandle from, InstructionHandle to) throws TargetLostException {
		remove(from.prev, to.next, false);
	}

	/**
	 * Remove instructions from instruction `from' to instruction `to' contained in this list. The user must ensure that `from' is
	 * an instruction before `to', or risk havoc. The corresponding Instruction handles must not be reused!
	 *
	 * @param from where to start deleting (inclusive)
	 * @param to where to end deleting (inclusive)
	 */
	public void delete(Instruction from, Instruction to) throws TargetLostException {
		InstructionHandle from_ih, to_ih;

		if ((from_ih = findInstruction1(from)) == null) {
			throw new ClassGenException("Instruction " + from + " is not contained in this list.");
		}

		if ((to_ih = findInstruction2(to)) == null) {
			throw new ClassGenException("Instruction " + to + " is not contained in this list.");
		}
		delete(from_ih, to_ih);
	}

	/**
	 * Search for given Instruction reference, start at beginning of list.
	 *
	 * @param i instruction to search for
	 * @return instruction found on success, null otherwise
	 */
	private InstructionHandle findInstruction1(Instruction i) {
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			if (ih.instruction == i) {
				return ih;
			}
		}

		return null;
	}

	/**
	 * Search for given Instruction reference, start at end of list
	 *
	 * @param i instruction to search for
	 * @return instruction found on success, null otherwise
	 */
	private InstructionHandle findInstruction2(Instruction i) {
		for (InstructionHandle ih = end; ih != null; ih = ih.prev) {
			if (ih.instruction == i) {
				return ih;
			}
		}

		return null;
	}

	public boolean contains(InstructionHandle i) {
		if (i == null) {
			return false;
		}

		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			if (ih == i) {
				return true;
			}
		}

		return false;
	}

	public boolean contains(Instruction i) {
		return findInstruction1(i) != null;
	}

	public void setPositions() {
		setPositions(false);
	}

	/**
	 * Give all instructions their position number (offset in byte stream), i.e., make the list ready to be dumped.
	 *
	 * @param check Perform sanity checks, e.g. if all targeted instructions really belong to this list
	 */
	public void setPositions(boolean check) {
		int maxAdditionalBytes = 0;
		int index = 0, count = 0;
		int[] pos = new int[length];

		// Pass 0: Sanity checks
		if (check) {
			checkInstructionList();
		}

		// Pass 1: Set position numbers and sum up the maximum number of bytes an
		// instruction may be shifted.
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			Instruction i = ih.instruction;
			ih.setPosition(index);
			pos[count++] = index;

			/*
			 * Get an estimate about how many additional bytes may be added, because BranchInstructions may have variable length
			 * depending on the target offset (short vs. int) or alignment issues (TABLESWITCH and LOOKUPSWITCH).
			 */
			switch (i.opcode) {
			case Constants.JSR:
			case Constants.GOTO:
				maxAdditionalBytes += 2;
				break;

			case Constants.TABLESWITCH:
			case Constants.LOOKUPSWITCH:
				maxAdditionalBytes += 3;
				break;
			}
			index += i.getLength();
		}

		// OPTIMIZE positions will only move around if there have been expanding instructions
		// if (max_additional_bytes==0...) {
		//
		// }

		/*
		 * Pass 2: Expand the variable-length (Branch)Instructions depending on the target offset (short or int) and ensure that
		 * branch targets are within this list.
		 */
		boolean nonZeroOffset = false;
		int offset = 0;
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			if (ih instanceof BranchHandle) {
				offset += ((BranchHandle) ih).updatePosition(offset, maxAdditionalBytes);
				if (offset != 0) {
					nonZeroOffset = true;
				}
			}
		}
		if (nonZeroOffset) {
			/*
			 * Pass 3: Update position numbers (which may have changed due to the preceding expansions), like pass 1.
			 */
			index = count = 0;
			for (InstructionHandle ih = start; ih != null; ih = ih.next) {
				Instruction i = ih.instruction;
				ih.setPosition(index);
				pos[count++] = index;
				index += i.getLength();
			}
		}

		positions = new int[count]; // Trim to proper size
		System.arraycopy(pos, 0, positions, 0, count);
	}

	private void checkInstructionList() {
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			Instruction i = ih.instruction;

			if (i instanceof InstructionBranch) { // target instruction within list?
				Instruction inst = ((InstructionBranch) i).getTarget().instruction;
				if (!contains(inst)) {
					throw new ClassGenException("Branch target of " + Constants.OPCODE_NAMES[i.opcode] + ":" + inst
							+ " not in instruction list");
				}

				if (i instanceof InstructionSelect) {
					InstructionHandle[] targets = ((InstructionSelect) i).getTargets();

					for (InstructionHandle target : targets) {
						inst = target.instruction;
						if (!contains(inst)) {
							throw new ClassGenException("Branch target of " + Constants.OPCODE_NAMES[i.opcode] + ":" + inst
									+ " not in instruction list");
						}
					}
				}

				if (!(ih instanceof BranchHandle)) {
					throw new ClassGenException("Branch instruction " + Constants.OPCODE_NAMES[i.opcode] + ":" + inst
							+ " not contained in BranchHandle.");
				}

			}
		}
	}

	/**
	 * When everything is finished, use this method to convert the instruction list into an array of bytes.
	 *
	 * @return the byte code ready to be dumped
	 */
	public byte[] getByteCode() {
		// Update position indices of instructions
		setPositions();

		ByteArrayOutputStream b = new ByteArrayOutputStream();
		DataOutputStream out = new DataOutputStream(b);

		try {
			for (InstructionHandle ih = start; ih != null; ih = ih.next) {
				Instruction i = ih.instruction;
				i.dump(out); // Traverse list
			}
		} catch (IOException e) {
			System.err.println(e);
			return null;
		}
		byte[] byteCode = b.toByteArray();
		if (byteCode.length > Constants.MAX_CODE_SIZE) {
			throw new ClassGenException("Code size too big: " + byteCode.length);
		}

		return byteCode;
	}

	/**
	 * @return an array of instructions without target information for branch instructions.
	 */
	public Instruction[] getInstructions() {
		ByteSequence bytes = new ByteSequence(getByteCode());
		List instructions = new ArrayList<>();

		try {
			while (bytes.available() > 0) {
				instructions.add(Instruction.readInstruction(bytes));
			}
		} catch (IOException e) {
			throw new ClassGenException(e.toString());
		}

		Instruction[] result = new Instruction[instructions.size()];
		instructions.toArray(result);
		return result;
	}

	@Override
	public String toString() {
		return toString(true);
	}

	/**
	 * @param verbose toggle output format
	 * @return String containing all instructions in this list.
	 */
	public String toString(boolean verbose) {
		StringBuilder buf = new StringBuilder();

		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			buf.append(ih.toString(verbose) + "\n");
		}

		return buf.toString();
	}

	/**
	 * @return Enumeration that lists all instructions (handles)
	 */
	public Iterator iterator() {
		return new Iterator() {
			private InstructionHandle ih = start;

			public Object next() {
				InstructionHandle i = ih;
				ih = ih.next;
				return i;
			}

			public void remove() {
				throw new UnsupportedOperationException();
			}

			public boolean hasNext() {
				return ih != null;
			}
		};
	}

	/**
	 * @return array containing all instructions (handles)
	 */
	public InstructionHandle[] getInstructionHandles() {
		InstructionHandle[] ihs = new InstructionHandle[length];
		InstructionHandle ih = start;

		for (int i = 0; i < length; i++) {
			ihs[i] = ih;
			ih = ih.next;
		}

		return ihs;
	}

	/**
	 * Get positions (offsets) of all instructions in the list. This relies on that the list has been freshly created from an byte
	 * code array, or that setPositions() has been called. Otherwise this may be inaccurate.
	 *
	 * @return array containing all instruction's offset in byte code
	 */
	public int[] getInstructionPositions() {
		return positions;
	}

	/**
	 * @return complete, i.e., deep copy of this list
	 */
	public InstructionList copy() {
		HashMap map = new HashMap<>();
		InstructionList il = new InstructionList();

		/*
		 * Pass 1: Make copies of all instructions, append them to the new list and associate old instruction references with the
		 * new ones, i.e., a 1:1 mapping.
		 */
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			Instruction i = ih.instruction;
			Instruction c = i.copy(); // Use clone for shallow copy

			if (c instanceof InstructionBranch) {
				map.put(ih, il.append((InstructionBranch) c));
			} else {
				map.put(ih, il.append(c));
			}
		}

		/*
		 * Pass 2: Update branch targets.
		 */
		InstructionHandle ih = start;
		InstructionHandle ch = il.start;

		while (ih != null) {
			Instruction i = ih.instruction;
			Instruction c = ch.instruction;

			if (i instanceof InstructionBranch) {
				InstructionBranch bi = (InstructionBranch) i;
				InstructionBranch bc = (InstructionBranch) c;
				InstructionHandle itarget = bi.getTarget(); // old target

				// New target is in hash map
				bc.setTarget(map.get(itarget));

				if (bi instanceof InstructionSelect) { // Either LOOKUPSWITCH or TABLESWITCH
					InstructionHandle[] itargets = ((InstructionSelect) bi).getTargets();
					InstructionHandle[] ctargets = ((InstructionSelect) bc).getTargets();

					for (int j = 0; j < itargets.length; j++) { // Update all targets
						ctargets[j] = map.get(itargets[j]);
					}
				}
			}

			ih = ih.next;
			ch = ch.next;
		}

		return il;
	}

	/**
	 * Replace all references to the old constant pool with references to the new constant pool
	 */
	public void replaceConstantPool(ConstantPool old_cp, ConstantPool new_cp) {
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			Instruction i = ih.instruction;
			if (i.isConstantPoolInstruction()) {
				InstructionCP ci = (InstructionCP) i;
				Constant c = old_cp.getConstant(ci.getIndex());
				ci.setIndex(new_cp.addConstant(c, old_cp));
			}
		}
	}

	private void clear() {
		start = end = null;
		length = 0;
	}

	/**
	 * Delete contents of list. Provides better memory utilization, because the system then may reuse the instruction handles. This
	 * method is typically called right after MethodGen.getMethod().
	 */
	public void dispose() {
		// Traverse in reverse order, because ih.next is overwritten
		for (InstructionHandle ih = end; ih != null; ih = ih.prev) {
			/*
			 * Causes BranchInstructions to release target and targeters, because it calls dispose() on the contained instruction.
			 */
			ih.dispose();
		}

		clear();
	}

	/**
	 * @return start of list
	 */
	public InstructionHandle getStart() {
		return start;
	}

	/**
	 * @return end of list
	 */
	public InstructionHandle getEnd() {
		return end;
	}

	/**
	 * @return length of list (Number of instructions, not bytes)
	 */
	public int getLength() {
		return length;
	}

	/**
	 * @return length of list (Number of instructions, not bytes)
	 */
	public int size() {
		return length;
	}

	/**
	 * Redirect all references from old_target to new_target, i.e., update targets of branch instructions.
	 *
	 * @param old_target the old target instruction handle
	 * @param new_target the new target instruction handle
	 */
	public void redirectBranches(InstructionHandle old_target, InstructionHandle new_target) {
		for (InstructionHandle ih = start; ih != null; ih = ih.next) {
			Instruction i = ih.getInstruction();

			if (i instanceof InstructionBranch) {
				InstructionBranch b = (InstructionBranch) i;
				InstructionHandle target = b.getTarget();

				if (target == old_target) {
					b.setTarget(new_target);
				}

				if (b instanceof InstructionSelect) { // Either LOOKUPSWITCH or TABLESWITCH
					InstructionHandle[] targets = ((InstructionSelect) b).getTargets();

					for (int j = 0; j < targets.length; j++) {
						if (targets[j] == old_target) {
							((InstructionSelect) b).setTarget(j, new_target);
						}
					}
				}
			}
		}
	}

	/**
	 * Redirect all references of local variables from old_target to new_target.
	 *
	 * @param lg array of local variables
	 * @param old_target the old target instruction handle
	 * @param new_target the new target instruction handle
	 * @see MethodGen
	 */
	public void redirectLocalVariables(LocalVariableGen[] lg, InstructionHandle old_target, InstructionHandle new_target) {
		for (LocalVariableGen localVariableGen : lg) {
			InstructionHandle start = localVariableGen.getStart();
			InstructionHandle end = localVariableGen.getEnd();

			if (start == old_target) {
				localVariableGen.setStart(new_target);
			}
			if (end == old_target) {
				localVariableGen.setEnd(new_target);
			}
		}
	}

	/**
	 * Redirect all references of exception handlers from old_target to new_target.
	 *
	 * @param exceptions array of exception handlers
	 * @param old_target the old target instruction handle
	 * @param new_target the new target instruction handle
	 * @see MethodGen
	 */
	public void redirectExceptionHandlers(CodeExceptionGen[] exceptions, InstructionHandle old_target, InstructionHandle new_target) {
		for (CodeExceptionGen exception : exceptions) {
			if (exception.getStartPC() == old_target) {
				exception.setStartPC(new_target);
			}

			if (exception.getEndPC() == old_target) {
				exception.setEndPC(new_target);
			}

			if (exception.getHandlerPC() == old_target) {
				exception.setHandlerPC(new_target);
			}
		}
	}

}