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  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(org.apache.bcel.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 == org.apache.bcel.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 = org.apache.bcel.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 }
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