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 * BranchHandle is returned by specialized InstructionList.append() whenever a BranchInstruction is appended. This is
021 * useful when the target of this instruction is not known at time of creation and must be set later via setTarget().
022 *
023 * @see InstructionHandle
024 * @see Instruction
025 * @see InstructionList
026 */
027public final class BranchHandle extends InstructionHandle {
028
029    /**
030     * Factory method.
031     */
032    static BranchHandle getBranchHandle(final BranchInstruction i) {
033        return new BranchHandle(i);
034    }
035
036    // This is also a cache in case the InstructionHandle#swapInstruction() method is used
037    // See BCEL-273
038    private BranchInstruction bi; // An alias in fact, but saves lots of casts
039
040    private BranchHandle(final BranchInstruction i) {
041        super(i);
042        bi = i;
043    }
044
045    /*
046     * Override InstructionHandle methods: delegate to branch instruction. Through this overriding all access to the private
047     * i_position field should be prevented.
048     */
049    @Override
050    public int getPosition() {
051        return bi.getPosition();
052    }
053
054    /**
055     * @return target of instruction.
056     */
057    public InstructionHandle getTarget() {
058        return bi.getTarget();
059    }
060
061    /**
062     * Sets new contents. Old instruction is disposed and may not be used anymore.
063     */
064    @Override // This is only done in order to apply the additional type check; could be merged with super impl.
065    public void setInstruction(final Instruction i) { // TODO could be package-protected?
066        super.setInstruction(i);
067        if (!(i instanceof BranchInstruction)) {
068            throw new ClassGenException("Assigning " + i + " to branch handle which is not a branch instruction");
069        }
070        bi = (BranchInstruction) i;
071    }
072
073    @Override
074    void setPosition(final int pos) {
075        // Original code: i_position = bi.position = pos;
076        bi.setPosition(pos);
077        super.setPosition(pos);
078    }
079
080    /**
081     * Pass new target to instruction.
082     */
083    public void setTarget(final InstructionHandle ih) {
084        bi.setTarget(ih);
085    }
086
087    @Override
088    protected int updatePosition(final int offset, final int maxOffset) {
089        final int x = bi.updatePosition(offset, maxOffset);
090        super.setPosition(bi.getPosition());
091        return x;
092    }
093
094    /**
095     * Update target of instruction.
096     */
097    public void updateTarget(final InstructionHandle oldIh, final InstructionHandle newIh) {
098        bi.updateTarget(oldIh, newIh);
099    }
100}