1   package org.apache.bcel.generic;
2   
3   /* ====================================================================
4    * The Apache Software License, Version 1.1
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7    * reserved.
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9    * Redistribution and use in source and binary forms, with or without
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21   * 3. The end-user documentation included with the redistribution,
22   *    if any, must include the following acknowledgment:
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25   *    Alternately, this acknowledgment may appear in the software itself,
26   *    if and wherever such third-party acknowledgments normally appear.
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51   * This software consists of voluntary contributions made by many
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55   */
56  
57  /*** 
58   * Super class for JSR - Jump to subroutine
59   *
60   * @version $Id: JsrInstruction.java,v 1.2 2002/08/07 18:01:32 mdahm Exp $
61   * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
62   */
63  public abstract class JsrInstruction extends BranchInstruction
64    implements UnconditionalBranch, TypedInstruction, StackProducer
65  {
66    JsrInstruction(short opcode, InstructionHandle target) {
67      super(opcode, target);
68    }
69  
70    /***
71     * Empty constructor needed for the Class.newInstance() statement in
72     * Instruction.readInstruction(). Not to be used otherwise.
73     */
74    JsrInstruction(){}
75  
76    /*** @return return address type
77     */
78    public Type getType(ConstantPoolGen cp) {
79      return new ReturnaddressType(physicalSuccessor());
80    }
81  
82    /***
83     * Returns an InstructionHandle to the physical successor
84     * of this JsrInstruction. <B>For this method to work,
85     * this JsrInstruction object must not be shared between
86     * multiple InstructionHandle objects!</B>
87     * Formally, there must not be InstructionHandle objects
88     * i, j where i != j and i.getInstruction() == this ==
89     * j.getInstruction().
90     * @return an InstructionHandle to the "next" instruction that
91     * will be executed when RETurned from a subroutine.
92     */
93    public InstructionHandle physicalSuccessor(){
94      InstructionHandle ih = this.target;
95      
96      // Rewind!
97      while(ih.getPrev() != null)
98        ih = ih.getPrev();
99      
100     // Find the handle for "this" JsrInstruction object.
101     while(ih.getInstruction() != this)
102       ih = ih.getNext();
103     
104     InstructionHandle toThis = ih;
105     
106     while(ih != null){
107     	ih = ih.getNext();
108     	if ((ih != null) && (ih.getInstruction() == this))
109         throw new RuntimeException("physicalSuccessor() called on a shared JsrInstruction.");
110     }
111     
112     // Return the physical successor		
113     return toThis.getNext();
114   }
115 }
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