commons-bcel-master/src/main/java/org/apache/bcel/generic/JsrInstruction.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.bcel.generic;

/**
 * Super class for JSR - Jump to subroutine
 */
public abstract class JsrInstruction extends BranchInstruction implements UnconditionalBranch, TypedInstruction, StackProducer {

    /**
     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
     */
    JsrInstruction() {
    }

    JsrInstruction(final short opcode, final InstructionHandle target) {
        super(opcode, target);
    }

    /**
     * @return return address type
     */
    @Override
    public Type getType(final ConstantPoolGen cp) {
        return new ReturnaddressType(physicalSuccessor());
    }

    /**
     * Returns an InstructionHandle to the physical successor of this JsrInstruction. <B>For this method to work, this
     * JsrInstruction object must not be shared between multiple InstructionHandle objects!</B> Formally, there must not be
     * InstructionHandle objects i, j where i != j and i.getInstruction() == this == j.getInstruction().
     *
     * @return an InstructionHandle to the "next" instruction that will be executed when RETurned from a subroutine.
     */
    public InstructionHandle physicalSuccessor() {
        InstructionHandle ih = super.getTarget();
        // Rewind!
        while (ih.getPrev() != null) {
            ih = ih.getPrev();
        }
        // Find the handle for "this" JsrInstruction object.
        while (ih.getInstruction() != this) {
            ih = ih.getNext();
        }
        final InstructionHandle toThis = ih;
        while (ih != null) {
            ih = ih.getNext();
            if (ih != null && ih.getInstruction() == this) {
                throw new IllegalStateException("physicalSuccessor() called on a shared JsrInstruction.");
            }
        }
        // Return the physical successor
        return toThis.getNext();
    }
}
