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Java > Open Source Codes > org > apache > bcel > generic > JsrInstruction


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 /**
20  * Super class for JSR - Jump to subroutine
21  *
22  * @version $Id: JsrInstruction.java 386056 2006-03-15 11:31:56Z tcurdt $
23  * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
24  */
25 public abstract class JsrInstruction extends BranchInstruction implements UnconditionalBranch,
26         TypedInstruction, StackProducer {
27
28     JsrInstruction(short opcode, InstructionHandle target) {
29         super(opcode, target);
30     }
31
32
33     /**
34      * Empty constructor needed for the Class.newInstance() statement in
35      * Instruction.readInstruction(). Not to be used otherwise.
36      */
37     JsrInstruction() {
38     }
39
40
41     /** @return return address type
42      */
43     public Type getType( ConstantPoolGen cp ) {
44         return new ReturnaddressType(physicalSuccessor());
45     }
46
47
48     /**
49      * Returns an InstructionHandle to the physical successor
50      * of this JsrInstruction. <B>For this method to work,
51      * this JsrInstruction object must not be shared between
52      * multiple InstructionHandle objects!</B>
53      * Formally, there must not be InstructionHandle objects
54      * i, j where i != j and i.getInstruction() == this ==
55      * j.getInstruction().
56      * @return an InstructionHandle to the "next" instruction that
57      * will be executed when RETurned from a subroutine.
58      */
59     public InstructionHandle physicalSuccessor() {
60         InstructionHandle ih = this.target;
61         // Rewind!
62 while (ih.getPrev() != null) {
63             ih = ih.getPrev();
64         }
65         // Find the handle for "this" JsrInstruction object.
66 while (ih.getInstruction() != this) {
67             ih = ih.getNext();
68         }
69         InstructionHandle toThis = ih;
70         while (ih != null) {
71             ih = ih.getNext();
72             if ((ih != null) && (ih.getInstruction() == this)) {
73                 throw new RuntimeException JavaDoc("physicalSuccessor() called on a shared JsrInstruction.");
74             }
75         }
76         // Return the physical successor
77 return toThis.getNext();
78     }
79 }
80
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