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 * @version $Id: GOTO.java 1749603 2016-06-21 20:50:19Z ggregory $
027 */
028public class GOTO extends GotoInstruction implements VariableLengthInstruction {
029
030    /**
031     * Empty constructor needed for the Class.newInstance() statement in
032     * Instruction.readInstruction(). Not to be used otherwise.
033     */
034    GOTO() {
035    }
036
037
038    public GOTO(final InstructionHandle target) {
039        super(org.apache.bcel.Const.GOTO, target);
040    }
041
042
043    /**
044     * Dump instruction as byte code to stream out.
045     * @param out Output stream
046     */
047    @Override
048    public void dump( final DataOutputStream out ) throws IOException {
049        super.setIndex(getTargetOffset());
050        final short _opcode = getOpcode();
051        if (_opcode == org.apache.bcel.Const.GOTO) {
052            super.dump(out);
053        } else { // GOTO_W
054            super.setIndex(getTargetOffset());
055            out.writeByte(_opcode);
056            out.writeInt(super.getIndex());
057        }
058    }
059
060
061    /**
062     * Called in pass 2 of InstructionList.setPositions() in order to update
063     * the branch target, that may shift due to variable length instructions.
064     *
065     * @param offset additional offset caused by preceding (variable length) instructions
066     * @param max_offset the maximum offset that may be caused by these instructions
067     * @return additional offset caused by possible change of this instruction's length
068     */
069    @Override
070    protected int updatePosition( final int offset, final int max_offset ) {
071        final int i = getTargetOffset(); // Depending on old position value
072        setPosition(getPosition() + offset); // Position may be shifted by preceding expansions
073        if (Math.abs(i) >= (Short.MAX_VALUE - max_offset)) { // to large for short (estimate)
074            super.setOpcode(org.apache.bcel.Const.GOTO_W);
075            final short old_length = (short) super.getLength();
076            super.setLength(5);
077            return super.getLength() - old_length;
078        }
079        return 0;
080    }
081
082
083    /**
084     * Call corresponding visitor method(s). The order is:
085     * Call visitor methods of implemented interfaces first, then
086     * call methods according to the class hierarchy in descending order,
087     * i.e., the most specific visitXXX() call comes last.
088     *
089     * @param v Visitor object
090     */
091    @Override
092    public void accept( final Visitor v ) {
093        v.visitVariableLengthInstruction(this);
094        v.visitUnconditionalBranch(this);
095        v.visitBranchInstruction(this);
096        v.visitGotoInstruction(this);
097        v.visitGOTO(this);
098    }
099}