View Javadoc
1   /*
2    * reserved comment block
3    * DO NOT REMOVE OR ALTER!
4    */
5   package com.sun.org.apache.bcel.internal.generic;
6   
7   /* ====================================================================
8    * The Apache Software License, Version 1.1
9    *
10   * Copyright (c) 2001 The Apache Software Foundation.  All rights
11   * reserved.
12   *
13   * Redistribution and use in source and binary forms, with or without
14   * modification, are permitted provided that the following conditions
15   * are met:
16   *
17   * 1. Redistributions of source code must retain the above copyright
18   *    notice, this list of conditions and the following disclaimer.
19   *
20   * 2. Redistributions in binary form must reproduce the above copyright
21   *    notice, this list of conditions and the following disclaimer in
22   *    the documentation and/or other materials provided with the
23   *    distribution.
24   *
25   * 3. The end-user documentation included with the redistribution,
26   *    if any, must include the following acknowledgment:
27   *       "This product includes software developed by the
28   *        Apache Software Foundation (http://www.apache.org/)."
29   *    Alternately, this acknowledgment may appear in the software itself,
30   *    if and wherever such third-party acknowledgments normally appear.
31   *
32   * 4. The names "Apache" and "Apache Software Foundation" and
33   *    "Apache BCEL" must not be used to endorse or promote products
34   *    derived from this software without prior written permission. For
35   *    written permission, please contact apache@apache.org.
36   *
37   * 5. Products derived from this software may not be called "Apache",
38   *    "Apache BCEL", nor may "Apache" appear in their name, without
39   *    prior written permission of the Apache Software Foundation.
40   *
41   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52   * SUCH DAMAGE.
53   * ====================================================================
54   *
55   * This software consists of voluntary contributions made by many
56   * individuals on behalf of the Apache Software Foundation.  For more
57   * information on the Apache Software Foundation, please see
58   * <http://www.apache.org/>.
59   */
60  import java.io.*;
61  
62  /**
63   * GOTO - Branch always (to relative offset, not absolute address)
64   *
65   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
66   */
67  public class GOTO extends GotoInstruction implements VariableLengthInstruction {
68    /**
69     * Empty constructor needed for the Class.newInstance() statement in
70     * Instruction.readInstruction(). Not to be used otherwise.
71     */
72    GOTO() {}
73  
74    public GOTO(InstructionHandle target) {
75      super(com.sun.org.apache.bcel.internal.Constants.GOTO, target);
76    }
77  
78    /**
79     * Dump instruction as byte code to stream out.
80     * @param out Output stream
81     */
82    public void dump(DataOutputStream out) throws IOException {
83      index = getTargetOffset();
84      if(opcode == com.sun.org.apache.bcel.internal.Constants.GOTO)
85        super.dump(out);
86      else { // GOTO_W
87        index = getTargetOffset();
88        out.writeByte(opcode);
89        out.writeInt(index);
90      }
91    }
92  
93    /** Called in pass 2 of InstructionList.setPositions() in order to update
94     * the branch target, that may shift due to variable length instructions.
95     */
96    protected int updatePosition(int offset, int max_offset) {
97      int i = getTargetOffset(); // Depending on old position value
98  
99      position += offset; // Position may be shifted by preceding expansions
100 
101     if(Math.abs(i) >= (32767 - max_offset)) { // to large for short (estimate)
102       opcode = com.sun.org.apache.bcel.internal.Constants.GOTO_W;
103       length = 5;
104       return 2; // 5 - 3
105     }
106 
107     return 0;
108   }
109 
110   /**
111    * Call corresponding visitor method(s). The order is:
112    * Call visitor methods of implemented interfaces first, then
113    * call methods according to the class hierarchy in descending order,
114    * i.e., the most specific visitXXX() call comes last.
115    *
116    * @param v Visitor object
117    */
118   public void accept(Visitor v) {
119     v.visitVariableLengthInstruction(this);
120     v.visitUnconditionalBranch(this);
121     v.visitBranchInstruction(this);
122     v.visitGotoInstruction(this);
123     v.visitGOTO(this);
124   }
125 }