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    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 maxOffset 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 maxOffset) {
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 - maxOffset) { // to large for short (estimate)
085            super.setOpcode(org.apache.bcel.Const.GOTO_W);
086            final short oldLength = (short) super.getLength();
087            super.setLength(5);
088            return super.getLength() - oldLength;
089        }
090        return 0;
091    }
092}