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1   /*
2    * Copyright  2000-2004 The Apache Software Foundation
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License"); 
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License. 
15   *
16   */
17  package org.apache.bcel.generic;
18  
19  import java.io.DataOutputStream;
20  import java.io.IOException;
21  import org.apache.bcel.util.ByteSequence;
22  
23  /*** 
24   * RET - Return from subroutine
25   *
26   * <PRE>Stack: ... -&gt; ...</PRE>
27   *
28   * @version $Id: RET.java 386056 2006-03-15 11:31:56Z tcurdt $
29   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
30   */
31  public class RET extends Instruction implements IndexedInstruction, TypedInstruction {
32  
33      private boolean wide;
34      private int index; // index to local variable containg the return address
35  
36  
37      /***
38       * Empty constructor needed for the Class.newInstance() statement in
39       * Instruction.readInstruction(). Not to be used otherwise.
40       */
41      RET() {
42      }
43  
44  
45      public RET(int index) {
46          super(org.apache.bcel.Constants.RET, (short) 2);
47          setIndex(index); // May set wide as side effect
48      }
49  
50  
51      /***
52       * Dump instruction as byte code to stream out.
53       * @param out Output stream
54       */
55      public void dump( DataOutputStream out ) throws IOException {
56          if (wide) {
57              out.writeByte(org.apache.bcel.Constants.WIDE);
58          }
59          out.writeByte(opcode);
60          if (wide) {
61              out.writeShort(index);
62          } else {
63              out.writeByte(index);
64          }
65      }
66  
67  
68      private final void setWide() {
69          wide = index > org.apache.bcel.Constants.MAX_BYTE;
70          if (wide) {
71              length = 4; // Including the wide byte  
72          } else {
73              length = 2;
74          }
75      }
76  
77  
78      /***
79       * Read needed data (e.g. index) from file.
80       */
81      protected void initFromFile( ByteSequence bytes, boolean wide ) throws IOException {
82          this.wide = wide;
83          if (wide) {
84              index = bytes.readUnsignedShort();
85              length = 4;
86          } else {
87              index = bytes.readUnsignedByte();
88              length = 2;
89          }
90      }
91  
92  
93      /***
94       * @return index of local variable containg the return address
95       */
96      public final int getIndex() {
97          return index;
98      }
99  
100 
101     /***
102      * Set index of local variable containg the return address
103      */
104     public final void setIndex( int n ) {
105         if (n < 0) {
106             throw new ClassGenException("Negative index value: " + n);
107         }
108         index = n;
109         setWide();
110     }
111 
112 
113     /***
114      * @return mnemonic for instruction
115      */
116     public String toString( boolean verbose ) {
117         return super.toString(verbose) + " " + index;
118     }
119 
120 
121     /*** @return return address type
122      */
123     public Type getType( ConstantPoolGen cp ) {
124         return ReturnaddressType.NO_TARGET;
125     }
126 
127 
128     /***
129      * Call corresponding visitor method(s). The order is:
130      * Call visitor methods of implemented interfaces first, then
131      * call methods according to the class hierarchy in descending order,
132      * i.e., the most specific visitXXX() call comes last.
133      *
134      * @param v Visitor object
135      */
136     public void accept( Visitor v ) {
137         v.visitRET(this);
138     }
139 }