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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  /**
21   * Super class for JSR - Jump to subroutine
22   *
23   * @version $Id: JsrInstruction.html 1021978 2017-12-09 17:38:21Z ggregory $
24   */
25  public abstract class JsrInstruction extends BranchInstruction implements UnconditionalBranch,
26          TypedInstruction, StackProducer {
27  
28      JsrInstruction(final short opcode, final InstructionHandle target) {
29          super(opcode, target);
30      }
31  
32  
33      /**
34       * Empty constructor needed for Instruction.readInstruction.
35       * Not to be used otherwise.
36       */
37      JsrInstruction() {
38      }
39  
40  
41      /** @return return address type
42       */
43      @Override
44      public Type getType( final ConstantPoolGen cp ) {
45          return new ReturnaddressType(physicalSuccessor());
46      }
47  
48  
49      /**
50       * Returns an InstructionHandle to the physical successor
51       * of this JsrInstruction. <B>For this method to work,
52       * this JsrInstruction object must not be shared between
53       * multiple InstructionHandle objects!</B>
54       * Formally, there must not be InstructionHandle objects
55       * i, j where i != j and i.getInstruction() == this ==
56       * j.getInstruction().
57       * @return an InstructionHandle to the "next" instruction that
58       * will be executed when RETurned from a subroutine.
59       */
60      public InstructionHandle physicalSuccessor() {
61          InstructionHandle ih = super.getTarget();
62          // Rewind!
63          while (ih.getPrev() != null) {
64              ih = ih.getPrev();
65          }
66          // Find the handle for "this" JsrInstruction object.
67          while (ih.getInstruction() != this) {
68              ih = ih.getNext();
69          }
70          final InstructionHandle toThis = ih;
71          while (ih != null) {
72              ih = ih.getNext();
73              if ((ih != null) && (ih.getInstruction() == this)) {
74                  throw new RuntimeException("physicalSuccessor() called on a shared JsrInstruction.");
75              }
76          }
77          // Return the physical successor
78          return toThis.getNext();
79      }
80  }