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  import org.apache.bcel.util.ByteSequence;
58  
59  /*** 
60   * RET - Return from subroutine
61   *
62   * <PRE>Stack: ..., -> ..., address</PRE>
63   *
64   * @version $Id: RET.java,v 1.1.1.1 2001/10/29 20:00:25 jvanzyl Exp $
65   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
66   */
67  public class RET extends Instruction implements IndexedInstruction, TypedInstruction {
68    private boolean wide;
69    private int     index; // index to local variable containg the return address
70  
71    /***
72     * Empty constructor needed for the Class.newInstance() statement in
73     * Instruction.readInstruction(). Not to be used otherwise.
74     */
75    RET() {}
76  
77    public RET(int index) {
78      super(org.apache.bcel.Constants.RET, (short)2);
79      setIndex(index);   // May set wide as side effect
80    }
81  
82    /***
83     * Dump instruction as byte code to stream out.
84     * @param out Output stream
85     */
86    public void dump(DataOutputStream out) throws IOException {
87      if(wide)
88        out.writeByte(org.apache.bcel.Constants.WIDE);
89  
90      out.writeByte(opcode);
91  
92      if(wide)
93        out.writeShort(index);
94      else
95        out.writeByte(index);
96    }
97  
98    private final void setWide() {
99      if(wide = index > org.apache.bcel.Constants.MAX_BYTE)
100       length = 4; // Including the wide byte  
101     else
102       length = 2;
103   }
104 
105   /***
106    * Read needed data (e.g. index) from file.
107    */
108   protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException
109   {
110     this.wide = wide;
111 
112     if(wide) {
113       index  = bytes.readUnsignedShort();
114       length = 4;
115     } else {
116       index = bytes.readUnsignedByte();
117       length = 2;
118     }
119   }
120 
121   /***
122    * @return index of local variable containg the return address
123    */
124   public final int getIndex() { return index; }
125 
126   /***
127    * Set index of local variable containg the return address
128    */
129   public final void setIndex(int n) { 
130     if(n < 0)
131       throw new ClassGenException("Negative index value: " + n);
132 
133     index = n;
134     setWide();
135   }
136 
137   /***
138    * @return mnemonic for instruction
139    */
140   public String toString(boolean verbose) {
141     return super.toString(verbose) + " " + index;
142   }  
143 
144   /*** @return return address type
145    */
146   public Type getType(ConstantPoolGen cp) {
147       return ReturnaddressType.NO_TARGET;
148   }
149 
150   /***
151    * Call corresponding visitor method(s). The order is:
152    * Call visitor methods of implemented interfaces first, then
153    * call methods according to the class hierarchy in descending order,
154    * i.e., the most specific visitXXX() call comes last.
155    *
156    * @param v Visitor object
157    */
158   public void accept(Visitor v) {
159     v.visitRET(this);
160   }
161 }
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