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 org.apache.bcel.Const;
021import org.apache.bcel.ExceptionConst;
022
023/**
024 * GETFIELD - Fetch field from object
025 * <PRE>Stack: ..., objectref -&gt; ..., value</PRE>
026 * OR
027 * <PRE>Stack: ..., objectref -&gt; ..., value.word1, value.word2</PRE>
028 *
029 */
030public class GETFIELD extends FieldInstruction implements ExceptionThrower, StackConsumer,
031        StackProducer {
032
033    /**
034     * Empty constructor needed for Instruction.readInstruction.
035     * Not to be used otherwise.
036     */
037    GETFIELD() {
038    }
039
040
041    public GETFIELD(final int index) {
042        super(Const.GETFIELD, index);
043    }
044
045
046    @Override
047    public int produceStack( final ConstantPoolGen cpg ) {
048        return getFieldSize(cpg);
049    }
050
051
052    @Override
053    public Class<?>[] getExceptions() {
054        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_FIELD_AND_METHOD_RESOLUTION,
055            ExceptionConst.NULL_POINTER_EXCEPTION,
056            ExceptionConst.INCOMPATIBLE_CLASS_CHANGE_ERROR);
057    }
058
059
060    /**
061     * Call corresponding visitor method(s). The order is:
062     * Call visitor methods of implemented interfaces first, then
063     * call methods according to the class hierarchy in descending order,
064     * i.e., the most specific visitXXX() call comes last.
065     *
066     * @param v Visitor object
067     */
068    @Override
069    public void accept( final Visitor v ) {
070        v.visitExceptionThrower(this);
071        v.visitStackConsumer(this);
072        v.visitStackProducer(this);
073        v.visitTypedInstruction(this);
074        v.visitLoadClass(this);
075        v.visitCPInstruction(this);
076        v.visitFieldOrMethod(this);
077        v.visitFieldInstruction(this);
078        v.visitGETFIELD(this);
079    }
080}