    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.bcel.generic;
    020
    021/**
    022 * BranchHandle is returned by specialized InstructionList.append() whenever a BranchInstruction is appended. This is
    023 * useful when the target of this instruction is not known at time of creation and must be set later via setTarget().
    024 *
    025 * @see InstructionHandle
    026 * @see Instruction
    027 * @see InstructionList
    028 */
    029public final class BranchHandle extends InstructionHandle {
    030
    031    /**
    032     * Factory method.
    033     */
    034    static BranchHandle getBranchHandle(final BranchInstruction i) {
    035        return new BranchHandle(i);
    036    }
    037
    038    // This is also a cache in case the InstructionHandle#swapInstruction() method is used
    039    // See BCEL-273
    040    private BranchInstruction bi; // An alias in fact, but saves lots of casts
    041
    042    private BranchHandle(final BranchInstruction i) {
    043        super(i);
    044        bi = i;
    045    }
    046
    047    /*
    048     * Override InstructionHandle methods: delegate to branch instruction. Through this overriding all access to the private
    049     * i_position field should be prevented.
    050     */
    051    @Override
    052    public int getPosition() {
    053        return bi.getPosition();
    054    }
    055
    056    /**
    057     * @return target of instruction.
    058     */
    059    public InstructionHandle getTarget() {
    060        return bi.getTarget();
    061    }
    062
    063    /**
    064     * Sets new contents. Old instruction is disposed and may not be used anymore.
    065     */
    066    @Override // This is only done in order to apply the additional type check; could be merged with super impl.
    067    public void setInstruction(final Instruction i) { // TODO could be package-protected?
    068        super.setInstruction(i);
    069        if (!(i instanceof BranchInstruction)) {
    070            throw new ClassGenException("Assigning " + i + " to branch handle which is not a branch instruction");
    071        }
    072        bi = (BranchInstruction) i;
    073    }
    074
    075    @Override
    076    void setPosition(final int pos) {
    077        // Original code: i_position = bi.position = pos;
    078        bi.setPosition(pos);
    079        super.setPosition(pos);
    080    }
    081
    082    /**
    083     * Pass new target to instruction.
    084     */
    085    public void setTarget(final InstructionHandle ih) {
    086        bi.setTarget(ih);
    087    }
    088
    089    @Override
    090    protected int updatePosition(final int offset, final int maxOffset) {
    091        final int x = bi.updatePosition(offset, maxOffset);
    092        super.setPosition(bi.getPosition());
    093        return x;
    094    }
    095
    096    /**
    097     * Update target of instruction.
    098     */
    099    public void updateTarget(final InstructionHandle oldIh, final InstructionHandle newIh) {
    100        bi.updateTarget(oldIh, newIh);
    101    }
    102}