001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.generic;
020
021/**
022 * Superclass for JSR - Jump to subroutine
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     * Gets the return address type.
038     *
039     * @return return address type.
040     */
041    @Override
042    public Type getType(final ConstantPoolGen cp) {
043        return new ReturnaddressType(physicalSuccessor());
044    }
045
046    /**
047     * Returns an InstructionHandle to the physical successor of this JsrInstruction. <B>For this method to work, this
048     * JsrInstruction object must not be shared between multiple InstructionHandle objects!</B> Formally, there must not be
049     * InstructionHandle objects i, j where i != j and i.getInstruction() == this == j.getInstruction().
050     *
051     * @return An InstructionHandle to the "next" instruction that will be executed when RETurned from a subroutine.
052     */
053    public InstructionHandle physicalSuccessor() {
054        InstructionHandle ih = super.getTarget();
055        // Rewind!
056        while (ih.getPrev() != null) {
057            ih = ih.getPrev();
058        }
059        // Find the handle for "this" JsrInstruction object.
060        while (ih.getInstruction() != this) {
061            ih = ih.getNext();
062        }
063        final InstructionHandle toThis = ih;
064        while (ih != null) {
065            ih = ih.getNext();
066            if (ih != null && ih.getInstruction() == this) {
067                throw new IllegalStateException("physicalSuccessor() called on a shared JsrInstruction.");
068            }
069        }
070        // Return the physical successor
071        return toThis.getNext();
072    }
073}