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


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.
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 import java.io.*;
57
58 /**
59  * GOTO - Branch always (to relative offset, not absolute address)
60  *
61  * @version $Id: GOTO.java,v 1.1.1.1 2001/10/29 20:00:13 jvanzyl Exp $
62  * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
63  */
64 public class GOTO extends GotoInstruction implements VariableLengthInstruction {
65   /**
66    * Empty constructor needed for the Class.newInstance() statement in
67    * Instruction.readInstruction(). Not to be used otherwise.
68    */
69   GOTO() {}
70
71   public GOTO(InstructionHandle target) {
72     super(com.sun.org.apache.bcel.internal.Constants.GOTO, target);
73   }
74
75   /**
76    * Dump instruction as byte code to stream out.
77    * @param out Output stream
78    */
79   public void dump(DataOutputStream out) throws IOException {
80     index = getTargetOffset();
81     if(opcode == com.sun.org.apache.bcel.internal.Constants.GOTO)
82       super.dump(out);
83     else { // GOTO_W
84 index = getTargetOffset();
85       out.writeByte(opcode);
86       out.writeInt(index);
87     }
88   }
89
90   /** Called in pass 2 of InstructionList.setPositions() in order to update
91    * the branch target, that may shift due to variable length instructions.
92    */
93   protected int updatePosition(int offset, int max_offset) {
94     int i = getTargetOffset(); // Depending on old position value
95
96     position += offset; // Position may be shifted by preceding expansions
97
98     if(Math.abs(i) >= (32767 - max_offset)) { // to large for short (estimate)
99 opcode = com.sun.org.apache.bcel.internal.Constants.GOTO_W;
100       length = 5;
101       return 2; // 5 - 3
102 }
103
104     return 0;
105   }
106
107   /**
108    * Call corresponding visitor method(s). The order is:
109    * Call visitor methods of implemented interfaces first, then
110    * call methods according to the class hierarchy in descending order,
111    * i.e., the most specific visitXXX() call comes last.
112    *
113    * @param v Visitor object
114    */
115   public void accept(Visitor v) {
116     v.visitVariableLengthInstruction(this);
117     v.visitUnconditionalBranch(this);
118     v.visitBranchInstruction(this);
119     v.visitGotoInstruction(this);
120     v.visitGOTO(this);
121   }
122 }
123
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