1 package org.apache.bcel.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.
32 *
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.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48 * SUCH DAMAGE.
49 * ====================================================================
50 *
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
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