    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}