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,
025        TypedInstruction, StackProducer {
026
027    JsrInstruction(final short opcode, final InstructionHandle target) {
028        super(opcode, target);
029    }
030
031
032    /**
033     * Empty constructor needed for Instruction.readInstruction.
034     * Not to be used otherwise.
035     */
036    JsrInstruction() {
037    }
038
039
040    /** @return return address type
041     */
042    @Override
043    public Type getType( final ConstantPoolGen cp ) {
044        return new ReturnaddressType(physicalSuccessor());
045    }
046
047
048    /**
049     * Returns an InstructionHandle to the physical successor
050     * of this JsrInstruction. <B>For this method to work,
051     * this JsrInstruction object must not be shared between
052     * multiple InstructionHandle objects!</B>
053     * Formally, there must not be InstructionHandle objects
054     * i, j where i != j and i.getInstruction() == this ==
055     * j.getInstruction().
056     * @return an InstructionHandle to the "next" instruction that
057     * will be executed when RETurned from a subroutine.
058     */
059    public InstructionHandle physicalSuccessor() {
060        InstructionHandle ih = super.getTarget();
061        // Rewind!
062        while (ih.getPrev() != null) {
063            ih = ih.getPrev();
064        }
065        // Find the handle for "this" JsrInstruction object.
066        while (ih.getInstruction() != this) {
067            ih = ih.getNext();
068        }
069        final InstructionHandle toThis = ih;
070        while (ih != null) {
071            ih = ih.getNext();
072            if ((ih != null) && (ih.getInstruction() == this)) {
073                throw new RuntimeException("physicalSuccessor() called on a shared JsrInstruction.");
074            }
075        }
076        // Return the physical successor
077        return toThis.getNext();
078    }
079}