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