1 /*
   2  * reserved comment block
   3  * DO NOT REMOVE OR ALTER!
   4  */
   5 /*
   6  * Licensed to the Apache Software Foundation (ASF) under one or more
   7  * contributor license agreements.  See the NOTICE file distributed with
   8  * this work for additional information regarding copyright ownership.
   9  * The ASF licenses this file to You under the Apache License, Version 2.0
  10  * (the "License"); you may not use this file except in compliance with
  11  * the License.  You may obtain a copy of the License at
  12  *
  13  *      http://www.apache.org/licenses/LICENSE-2.0
  14  *
  15  * Unless required by applicable law or agreed to in writing, software
  16  * distributed under the License is distributed on an "AS IS" BASIS,
  17  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  18  * See the License for the specific language governing permissions and
  19  * limitations under the License.
  20  */
  21 
  22 package com.sun.org.apache.bcel.internal.generic;
  23 
  24 
  25 /**
  26  * Super class for JSR - Jump to subroutine
  27  *
  28  * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
  29  */
  30 public abstract class JsrInstruction extends BranchInstruction
  31   implements UnconditionalBranch, TypedInstruction, StackProducer
  32 {
  33   JsrInstruction(short opcode, InstructionHandle target) {
  34     super(opcode, target);
  35   }
  36 
  37   /**
  38    * Empty constructor needed for the Class.newInstance() statement in
  39    * Instruction.readInstruction(). Not to be used otherwise.
  40    */
  41   JsrInstruction(){}
  42 
  43   /** @return return address type
  44    */
  45   public Type getType(ConstantPoolGen cp) {
  46     return new ReturnaddressType(physicalSuccessor());
  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 = this.target;
  62 
  63     // Rewind!
  64     while(ih.getPrev() != null)
  65       ih = ih.getPrev();
  66 
  67     // Find the handle for "this" JsrInstruction object.
  68     while(ih.getInstruction() != this)
  69       ih = ih.getNext();
  70 
  71     InstructionHandle toThis = ih;
  72 
  73     while(ih != null){
  74         ih = ih.getNext();
  75         if ((ih != null) && (ih.getInstruction() == this))
  76         throw new RuntimeException("physicalSuccessor() called on a shared JsrInstruction.");
  77     }
  78 
  79     // Return the physical successor
  80     return toThis.getNext();
  81   }
  82 }