/*
 * 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
 *
 *   https://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();
    }
}
