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}