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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  package org.apache.bcel.generic;
19  
20  import java.io.DataOutputStream;
21  import java.io.IOException;
22  
23  import org.apache.bcel.util.ByteSequence;
24  
25  /**
26   * RET - Return from subroutine
27   *
28   * <PRE>Stack: ... -&gt; ...</PRE>
29   *
30   * @version $Id: RET.html 1021978 2017-12-09 17:38:21Z ggregory $
31   */
32  public class RET extends Instruction implements IndexedInstruction, TypedInstruction {
33  
34      private boolean wide;
35      private int index; // index to local variable containg the return address
36  
37  
38      /**
39       * Empty constructor needed for Instruction.readInstruction.
40       * Not to be used otherwise.
41       */
42      RET() {
43      }
44  
45  
46      public RET(final int index) {
47          super(org.apache.bcel.Const.RET, (short) 2);
48          setIndex(index); // May set wide as side effect
49      }
50  
51  
52      /**
53       * Dump instruction as byte code to stream out.
54       * @param out Output stream
55       */
56      @Override
57      public void dump( final DataOutputStream out ) throws IOException {
58          if (wide) {
59              out.writeByte(org.apache.bcel.Const.WIDE);
60          }
61          out.writeByte(super.getOpcode());
62          if (wide) {
63              out.writeShort(index);
64          } else {
65              out.writeByte(index);
66          }
67      }
68  
69  
70      private void setWide() {
71          wide = index > org.apache.bcel.Const.MAX_BYTE;
72          if (wide) {
73              super.setLength(4); // Including the wide byte
74          } else {
75              super.setLength(2);
76          }
77      }
78  
79  
80      /**
81       * Read needed data (e.g. index) from file.
82       */
83      @Override
84      protected void initFromFile( final ByteSequence bytes, final boolean wide ) throws IOException {
85          this.wide = wide;
86          if (wide) {
87              index = bytes.readUnsignedShort();
88              super.setLength(4);
89          } else {
90              index = bytes.readUnsignedByte();
91              super.setLength(2);
92          }
93      }
94  
95  
96      /**
97       * @return index of local variable containg the return address
98       */
99      @Override
100     public final int getIndex() {
101         return index;
102     }
103 
104 
105     /**
106      * Set index of local variable containg the return address
107      */
108     @Override
109     public final void setIndex( final int n ) {
110         if (n < 0) {
111             throw new ClassGenException("Negative index value: " + n);
112         }
113         index = n;
114         setWide();
115     }
116 
117 
118     /**
119      * @return mnemonic for instruction
120      */
121     @Override
122     public String toString( final boolean verbose ) {
123         return super.toString(verbose) + " " + index;
124     }
125 
126 
127     /** @return return address type
128      */
129     @Override
130     public Type getType( final ConstantPoolGen cp ) {
131         return ReturnaddressType.NO_TARGET;
132     }
133 
134 
135     /**
136      * Call corresponding visitor method(s). The order is:
137      * Call visitor methods of implemented interfaces first, then
138      * call methods according to the class hierarchy in descending order,
139      * i.e., the most specific visitXXX() call comes last.
140      *
141      * @param v Visitor object
142      */
143     @Override
144     public void accept( final Visitor v ) {
145         v.visitRET(this);
146     }
147 }