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Java > Open Source Codes > com > sun > org > apache > bcel > internal > generic > BranchHandle


1 package com.sun.org.apache.bcel.internal.generic;
2
3 /* ====================================================================
4  * The Apache Software License, Version 1.1
5  *
6  * Copyright (c) 2001 The Apache Software Foundation. All rights
7  * reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright
14  * notice, this list of conditions and the following disclaimer.
15  *
16  * 2. Redistributions in binary form must reproduce the above copyright
17  * notice, this list of conditions and the following disclaimer in
18  * the documentation and/or other materials provided with the
19  * distribution.
20  *
21  * 3. The end-user documentation included with the redistribution,
22  * if any, must include the following acknowledgment:
23  * "This product includes software developed by the
24  * Apache Software Foundation (http://www.apache.org/)."
25  * Alternately, this acknowledgment may appear in the software itself,
26  * if and wherever such third-party acknowledgments normally appear.
27  *
28  * 4. The names "Apache" and "Apache Software Foundation" and
29  * "Apache BCEL" must not be used to endorse or promote products
30  * derived from this software without prior written permission. For
31  * written permission, please contact apache@apache.org.
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33  * 5. Products derived from this software may not be called "Apache",
34  * "Apache BCEL", nor may "Apache" appear in their name, without
35  * prior written permission of the Apache Software Foundation.
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37  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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41  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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43  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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45  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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51  * This software consists of voluntary contributions made by many
52  * individuals on behalf of the Apache Software Foundation. For more
53  * information on the Apache Software Foundation, please see
54  * <http://www.apache.org/>.
55  */
56
57 /**
58  * BranchHandle is returned by specialized InstructionList.append() whenever a
59  * BranchInstruction is appended. This is useful when the target of this
60  * instruction is not known at time of creation and must be set later
61  * via setTarget().
62  *
63  * @see InstructionHandle
64  * @see Instruction
65  * @see InstructionList
66  * @version $Id: BranchHandle.java,v 1.1.1.1 2001/10/29 20:00:06 jvanzyl Exp $
67  * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
68  */
69 public final class BranchHandle extends InstructionHandle {
70   private BranchInstruction bi; // An alias in fact, but saves lots of casts
71
72   private BranchHandle(BranchInstruction i) {
73     super(i);
74     bi = i;
75   }
76
77   /** Factory methods.
78    */
79   private static BranchHandle bh_list = null; // List of reusable handles
80
81   static final BranchHandle getBranchHandle(BranchInstruction i) {
82     if(bh_list == null)
83       return new BranchHandle(i);
84     else {
85       BranchHandle bh = bh_list;
86       bh_list = (BranchHandle)bh.next;
87
88       bh.setInstruction(i);
89
90       return bh;
91     }
92   }
93   
94   /** Handle adds itself to the list of resuable handles.
95    */
96   protected void addHandle() {
97     next = bh_list;
98     bh_list = this;
99   }
100
101   /* Override InstructionHandle methods: delegate to branch instruction.
102    * Through this overriding all access to the private i_position field should
103    * be prevented.
104    */
105   public int getPosition() { return bi.position; }
106
107   void setPosition(int pos) {
108     i_position = bi.position = pos;
109   }
110
111   protected int updatePosition(int offset, int max_offset) {
112     int x = bi.updatePosition(offset, max_offset);
113     i_position = bi.position;
114     return x;
115   }
116
117   /**
118    * Pass new target to instruction.
119    */
120   public void setTarget(InstructionHandle ih) {
121     bi.setTarget(ih);
122   }
123
124   /**
125    * Update target of instruction.
126    */
127   public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
128     bi.updateTarget(old_ih, new_ih);
129   }
130
131   /**
132    * @return target of instruction.
133    */
134   public InstructionHandle getTarget() {
135     return bi.getTarget();
136   }
137
138   /**
139    * Set new contents. Old instruction is disposed and may not be used anymore.
140    */
141   public void setInstruction(Instruction i) {
142     super.setInstruction(i);
143
144     if(!(i instanceof BranchInstruction))
145       throw new ClassGenException("Assigning " + i +
146                   " to branch handle which is not a branch instruction");
147
148     bi = (BranchInstruction)i;
149   }
150 }
151
152
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