    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
    019import java.io.DataOutputStream;
    020import java.io.IOException;
    021
    022/**
    023 * GOTO - Branch always (to relative offset, not absolute address)
    024 */
    025public class GOTO extends GotoInstruction implements VariableLengthInstruction {
    026
    027    /**
    028     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
    029     */
    030    GOTO() {
    031    }
    032
    033    public GOTO(final InstructionHandle target) {
    034        super(org.apache.bcel.Const.GOTO, target);
    035    }
    036
    037    /**
    038     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    039     * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
    040     *
    041     * @param v Visitor object
    042     */
    043    @Override
    044    public void accept(final Visitor v) {
    045        v.visitVariableLengthInstruction(this);
    046        v.visitUnconditionalBranch(this);
    047        v.visitBranchInstruction(this);
    048        v.visitGotoInstruction(this);
    049        v.visitGOTO(this);
    050    }
    051
    052    /**
    053     * Dump instruction as byte code to stream out.
    054     *
    055     * @param out Output stream
    056     */
    057    @Override
    058    public void dump(final DataOutputStream out) throws IOException {
    059        super.setIndex(getTargetOffset());
    060        final short opcode = getOpcode();
    061        if (opcode == org.apache.bcel.Const.GOTO) {
    062            super.dump(out);
    063        } else { // GOTO_W
    064            super.setIndex(getTargetOffset());
    065            out.writeByte(opcode);
    066            out.writeInt(super.getIndex());
    067        }
    068    }
    069
    070    /**
    071     * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to
    072     * variable length instructions.
    073     *
    074     * @param offset additional offset caused by preceding (variable length) instructions
    075     * @param maxOffset the maximum offset that may be caused by these instructions
    076     * @return additional offset caused by possible change of this instruction's length
    077     */
    078    @Override
    079    protected int updatePosition(final int offset, final int maxOffset) {
    080        final int i = getTargetOffset(); // Depending on old position value
    081        setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
    082        if (Math.abs(i) >= Short.MAX_VALUE - maxOffset) { // to large for short (estimate)
    083            super.setOpcode(org.apache.bcel.Const.GOTO_W);
    084            final short oldLength = (short) super.getLength();
    085            super.setLength(5);
    086            return super.getLength() - oldLength;
    087        }
    088        return 0;
    089    }
    090}