001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.generic;
019
020/**
021 * Super class for JSR - Jump to subroutine
022 *
023 */
024public abstract class JsrInstruction extends BranchInstruction implements UnconditionalBranch, TypedInstruction, StackProducer {
025
026    /**
027     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
028     */
029    JsrInstruction() {
030    }
031
032    JsrInstruction(final short opcode, final InstructionHandle target) {
033        super(opcode, target);
034    }
035
036    /**
037     * @return return address type
038     */
039    @Override
040    public Type getType(final ConstantPoolGen cp) {
041        return new ReturnaddressType(physicalSuccessor());
042    }
043
044    /**
045     * Returns an InstructionHandle to the physical successor of this JsrInstruction. <B>For this method to work, this
046     * JsrInstruction object must not be shared between multiple InstructionHandle objects!</B> Formally, there must not be
047     * InstructionHandle objects i, j where i != j and i.getInstruction() == this == j.getInstruction().
048     *
049     * @return an InstructionHandle to the "next" instruction that will be executed when RETurned from a subroutine.
050     */
051    public InstructionHandle physicalSuccessor() {
052        InstructionHandle ih = super.getTarget();
053        // Rewind!
054        while (ih.getPrev() != null) {
055            ih = ih.getPrev();
056        }
057        // Find the handle for "this" JsrInstruction object.
058        while (ih.getInstruction() != this) {
059            ih = ih.getNext();
060        }
061        final InstructionHandle toThis = ih;
062        while (ih != null) {
063            ih = ih.getNext();
064            if (ih != null && ih.getInstruction() == this) {
065                throw new IllegalStateException("physicalSuccessor() called on a shared JsrInstruction.");
066            }
067        }
068        // Return the physical successor
069        return toThis.getNext();
070    }
071}