Java tutorial
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. 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For more * information on the Apache Software Foundation, please see * <http://www.apache.org/>. */ import java.util.Collections; import java.util.HashSet; import java.util.Set; import org.aspectj.apache.bcel.classfile.Utility; /** * Instances of this class give users a handle to the instructions contained in an InstructionList. Instruction objects may be used * more than once within a list, this is useful because it saves memory and may be much faster. * * Within an InstructionList an InstructionHandle object is wrapped around all instructions, i.e., it implements a cell in a * doubly-linked list. From the outside only the next and the previous instruction (handle) are accessible. One can traverse the * list via an Enumeration returned by InstructionList.elements(). * * @version $Id: InstructionHandle.java,v 1.9 2009/10/05 17:35:36 aclement Exp $ * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> * @see Instruction * @see BranchHandle * @see InstructionList */ public class InstructionHandle implements java.io.Serializable { InstructionHandle next, prev; // Will be set from the outside Instruction instruction; protected int pos = -1; // byte code offset of instruction private Set<InstructionTargeter> targeters = Collections.emptySet(); protected InstructionHandle(Instruction i) { setInstruction(i); } static final InstructionHandle getInstructionHandle(Instruction i) { return new InstructionHandle(i); } public final InstructionHandle getNext() { return next; } public final InstructionHandle getPrev() { return prev; } public final Instruction getInstruction() { return instruction; } /** * Replace current instruction contained in this handle. Old instruction is disposed using Instruction.dispose(). */ public void setInstruction(Instruction i) { // Overridden in BranchHandle if (instruction != null) { instruction.dispose(); } instruction = i; } /** * @return the position, i.e., the byte code offset of the contained instruction. This is accurate only after * InstructionList.setPositions() has been called. */ public int getPosition() { return pos; } /** * Set the position, i.e., the byte code offset of the contained instruction. */ void setPosition(int pos) { this.pos = pos; } /** * Delete contents, i.e., remove user access and make handle reusable. */ // OPTIMIZE get rid of this? why do we need it void dispose() { next = prev = null; instruction.dispose(); instruction = null; pos = -1; removeAllTargeters(); } /** * Remove all targeters, if any. */ public void removeAllTargeters() { targeters.clear(); } /** * Denote this handle isn't referenced anymore by t. */ public void removeTargeter(InstructionTargeter t) { targeters.remove(t); } /** * Denote this handle is being referenced by t. */ public void addTargeter(InstructionTargeter t) { if (targeters == Collections.EMPTY_SET) { targeters = new HashSet<InstructionTargeter>(); } targeters.add(t); } public boolean hasTargeters() { return !targeters.isEmpty(); } public Set<InstructionTargeter> getTargeters() { return targeters; } public Set<InstructionTargeter> getTargetersCopy() { Set<InstructionTargeter> copy = new HashSet<InstructionTargeter>(); copy.addAll(targeters); return copy; } /** * @return a (verbose) string representation of the contained instruction. */ public String toString(boolean verbose) { return Utility.format(pos, 4, false, ' ') + ": " + instruction.toString(verbose); } public String toString() { return toString(true); } }