    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 $Id$
    027 */
    028public class GOTO extends GotoInstruction implements VariableLengthInstruction {
    029
    030    /**
    031     * Empty constructor needed for Instruction.readInstruction.
    032     * 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}