JsrInstruction xref

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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  /***
    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("physicalSuccessor() called on a shared JsrInstruction.");
    74              }
    75          }
    76          // Return the physical successor
    77          return toThis.getNext();
    78      }
    79  }