    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 *
    017 */
    018package org.apache.bcel.generic;
    019
    020/**
    021 * BranchHandle is returned by specialized InstructionList.append() whenever a
    022 * BranchInstruction is appended. This is useful when the target of this
    023 * instruction is not known at time of creation and must be set later
    024 * via setTarget().
    025 *
    026 * @see InstructionHandle
    027 * @see Instruction
    028 * @see InstructionList
    029 * @version $Id$
    030 */
    031public final class BranchHandle extends InstructionHandle {
    032
    033    // This is also a cache in case the InstructionHandle#swapInstruction() method is used
    034    // See BCEL-273
    035    private BranchInstruction bi; // An alias in fact, but saves lots of casts
    036
    037
    038    private BranchHandle(final BranchInstruction i) {
    039        super(i);
    040        bi = i;
    041    }
    042
    043    /** Factory method.
    044     */
    045    static BranchHandle getBranchHandle( final BranchInstruction i ) {
    046        return new BranchHandle(i);
    047    }
    048
    049
    050    /* Override InstructionHandle methods: delegate to branch instruction.
    051     * Through this overriding all access to the private i_position field should
    052     * be prevented.
    053     */
    054    @Override
    055    public int getPosition() {
    056        return bi.getPosition();
    057    }
    058
    059
    060    @Override
    061    void setPosition( final int pos ) {
    062        // Original code: i_position = bi.position = pos;
    063        bi.setPosition(pos);
    064        super.setPosition(pos);
    065    }
    066
    067
    068    @Override
    069    protected int updatePosition( final int offset, final int max_offset ) {
    070        final int x = bi.updatePosition(offset, max_offset);
    071        super.setPosition(bi.getPosition());
    072        return x;
    073    }
    074
    075
    076    /**
    077     * Pass new target to instruction.
    078     */
    079    public void setTarget( final InstructionHandle ih ) {
    080        bi.setTarget(ih);
    081    }
    082
    083
    084    /**
    085     * Update target of instruction.
    086     */
    087    public void updateTarget( final InstructionHandle old_ih, final InstructionHandle new_ih ) {
    088        bi.updateTarget(old_ih, new_ih);
    089    }
    090
    091
    092    /**
    093     * @return target of instruction.
    094     */
    095    public InstructionHandle getTarget() {
    096        return bi.getTarget();
    097    }
    098
    099
    100    /**
    101     * Set new contents. Old instruction is disposed and may not be used anymore.
    102     */
    103    @Override // This is only done in order to apply the additional type check; could be merged with super impl.
    104    public void setInstruction( final Instruction i ) { // TODO could be package-protected?
    105        super.setInstruction(i);
    106        if (!(i instanceof BranchInstruction)) {
    107            throw new ClassGenException("Assigning " + i
    108                    + " to branch handle which is not a branch instruction");
    109        }
    110        bi = (BranchInstruction) i;
    111    }
    112}