    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
    021import java.io.DataOutputStream;
    022import java.io.IOException;
    023
    024/**
    025 * GOTO - Branch always (to relative offset, not absolute address)
    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    /**
    036     * Constructs a GOTO instruction.
    037     *
    038     * @param target the target instruction.
    039     */
    040    public GOTO(final InstructionHandle target) {
    041        super(org.apache.bcel.Const.GOTO, target);
    042    }
    043
    044    /**
    045     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    046     * methods according to the class hierarchy in descending order, that is, the most specific visitXXX() call comes last.
    047     *
    048     * @param v Visitor object.
    049     */
    050    @Override
    051    public void accept(final Visitor v) {
    052        v.visitVariableLengthInstruction(this);
    053        v.visitUnconditionalBranch(this);
    054        v.visitBranchInstruction(this);
    055        v.visitGotoInstruction(this);
    056        v.visitGOTO(this);
    057    }
    058
    059    /**
    060     * Dumps instruction as byte code to stream out.
    061     *
    062     * @param out Output stream.
    063     */
    064    @Override
    065    public void dump(final DataOutputStream out) throws IOException {
    066        super.setIndex(getTargetOffset());
    067        final short opcode = getOpcode();
    068        if (opcode == org.apache.bcel.Const.GOTO) {
    069            super.dump(out);
    070        } else { // GOTO_W
    071            super.setIndex(getTargetOffset());
    072            out.writeByte(opcode);
    073            out.writeInt(super.getIndex());
    074        }
    075    }
    076
    077    /**
    078     * Called in pass 2 of InstructionList.setPositions() in order to update the branch target, that may shift due to
    079     * variable length instructions.
    080     *
    081     * @param offset additional offset caused by preceding (variable length) instructions.
    082     * @param maxOffset the maximum offset that may be caused by these instructions.
    083     * @return additional offset caused by possible change of this instruction's length.
    084     */
    085    @Override
    086    protected int updatePosition(final int offset, final int maxOffset) {
    087        final int i = getTargetOffset(); // Depending on old position value
    088        setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
    089        if (Math.abs(i) >= Short.MAX_VALUE - maxOffset) { // to large for short (estimate)
    090            super.setOpcode(org.apache.bcel.Const.GOTO_W);
    091            final short oldLength = (short) super.getLength();
    092            super.setLength(5);
    093            return super.getLength() - oldLength;
    094        }
    095        return 0;
    096    }
    097}