    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 * Super class 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     * @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}