    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
    020import java.io.DataOutputStream;
    021import java.io.IOException;
    022
    023/**
    024 * GOTO - Branch always (to relative offset, not absolute address)
    025 *
    026 */
    027public class GOTO extends GotoInstruction implements VariableLengthInstruction {
    028
    029    /**
    030     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
    031     */
    032    GOTO() {
    033    }
    034
    035    public GOTO(final InstructionHandle target) {
    036        super(org.apache.bcel.Const.GOTO, target);
    037    }
    038
    039    /**
    040     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    041     * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
    042     *
    043     * @param v Visitor object
    044     */
    045    @Override
    046    public void accept(final Visitor v) {
    047        v.visitVariableLengthInstruction(this);
    048        v.visitUnconditionalBranch(this);
    049        v.visitBranchInstruction(this);
    050        v.visitGotoInstruction(this);
    051        v.visitGOTO(this);
    052    }
    053
    054    /**
    055     * Dump instruction as byte code to stream out.
    056     *
    057     * @param out Output stream
    058     */
    059    @Override
    060    public void dump(final DataOutputStream out) throws IOException {
    061        super.setIndex(getTargetOffset());
    062        final short opcode = getOpcode();
    063        if (opcode == org.apache.bcel.Const.GOTO) {
    064            super.dump(out);
    065        } else { // GOTO_W
    066            super.setIndex(getTargetOffset());
    067            out.writeByte(opcode);
    068            out.writeInt(super.getIndex());
    069        }
    070    }
    071
    072    /**
    073     * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to
    074     * variable length instructions.
    075     *
    076     * @param offset additional offset caused by preceding (variable length) instructions
    077     * @param max_offset the maximum offset that may be caused by these instructions
    078     * @return additional offset caused by possible change of this instruction's length
    079     */
    080    @Override
    081    protected int updatePosition(final int offset, final int max_offset) {
    082        final int i = getTargetOffset(); // Depending on old position value
    083        setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
    084        if (Math.abs(i) >= Short.MAX_VALUE - max_offset) { // to large for short (estimate)
    085            super.setOpcode(org.apache.bcel.Const.GOTO_W);
    086            final short old_length = (short) super.getLength();
    087            super.setLength(5);
    088            return super.getLength() - old_length;
    089        }
    090        return 0;
    091    }
    092}