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 */
017package org.apache.bcel.generic;
018
019/**
020 * Super class for JSR - Jump to subroutine
021 */
022public abstract class JsrInstruction extends BranchInstruction implements UnconditionalBranch, TypedInstruction, StackProducer {
023
024    /**
025     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
026     */
027    JsrInstruction() {
028    }
029
030    JsrInstruction(final short opcode, final InstructionHandle target) {
031        super(opcode, target);
032    }
033
034    /**
035     * @return return address type
036     */
037    @Override
038    public Type getType(final ConstantPoolGen cp) {
039        return new ReturnaddressType(physicalSuccessor());
040    }
041
042    /**
043     * Returns an InstructionHandle to the physical successor of this JsrInstruction. <B>For this method to work, this
044     * JsrInstruction object must not be shared between multiple InstructionHandle objects!</B> Formally, there must not be
045     * InstructionHandle objects i, j where i != j and i.getInstruction() == this == j.getInstruction().
046     *
047     * @return an InstructionHandle to the "next" instruction that will be executed when RETurned from a subroutine.
048     */
049    public InstructionHandle physicalSuccessor() {
050        InstructionHandle ih = super.getTarget();
051        // Rewind!
052        while (ih.getPrev() != null) {
053            ih = ih.getPrev();
054        }
055        // Find the handle for "this" JsrInstruction object.
056        while (ih.getInstruction() != this) {
057            ih = ih.getNext();
058        }
059        final InstructionHandle toThis = ih;
060        while (ih != null) {
061            ih = ih.getNext();
062            if (ih != null && ih.getInstruction() == this) {
063                throw new IllegalStateException("physicalSuccessor() called on a shared JsrInstruction.");
064            }
065        }
066        // Return the physical successor
067        return toThis.getNext();
068    }
069}