    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
    023import org.apache.bcel.ExceptionConst;
    024import org.apache.bcel.util.ByteSequence;
    025
    026/**
    027 * LDC - Push item from constant pool.
    028 *
    029 * <PRE>Stack: ... -&gt; ..., item</PRE>
    030 *
    031 * @version $Id$
    032 */
    033public class LDC extends CPInstruction implements PushInstruction, ExceptionThrower {
    034
    035    /**
    036     * Empty constructor needed for Instruction.readInstruction.
    037     * Not to be used otherwise.
    038     */
    039    LDC() {
    040    }
    041
    042
    043    public LDC(final int index) {
    044        super(org.apache.bcel.Const.LDC_W, index);
    045        setSize();
    046    }
    047
    048
    049    // Adjust to proper size
    050    protected final void setSize() {
    051        if (super.getIndex() <= org.apache.bcel.Const.MAX_BYTE) { // Fits in one byte?
    052            super.setOpcode(org.apache.bcel.Const.LDC);
    053            super.setLength(2);
    054        } else {
    055            super.setOpcode(org.apache.bcel.Const.LDC_W);
    056            super.setLength(3);
    057        }
    058    }
    059
    060
    061    /**
    062     * Dump instruction as byte code to stream out.
    063     * @param out Output stream
    064     */
    065    @Override
    066    public void dump( final DataOutputStream out ) throws IOException {
    067        out.writeByte(super.getOpcode());
    068        if (super.getLength() == 2) { // TODO useless check?
    069            out.writeByte(super.getIndex());
    070        } else {
    071            out.writeShort(super.getIndex());
    072        }
    073    }
    074
    075
    076    /**
    077     * Set the index to constant pool and adjust size.
    078     */
    079    @Override
    080    public final void setIndex( final int index ) {
    081        super.setIndex(index);
    082        setSize();
    083    }
    084
    085
    086    /**
    087     * Read needed data (e.g. index) from file.
    088     */
    089    @Override
    090    protected void initFromFile( final ByteSequence bytes, final boolean wide ) throws IOException {
    091        super.setLength(2);
    092        super.setIndex(bytes.readUnsignedByte());
    093    }
    094
    095
    096    public Object getValue( final ConstantPoolGen cpg ) {
    097        org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(super.getIndex());
    098        switch (c.getTag()) {
    099            case org.apache.bcel.Const.CONSTANT_String:
    100                final int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex();
    101                c = cpg.getConstantPool().getConstant(i);
    102                return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
    103            case org.apache.bcel.Const.CONSTANT_Float:
    104                return new Float(((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
    105            case org.apache.bcel.Const.CONSTANT_Integer:
    106                return Integer.valueOf(((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
    107            case org.apache.bcel.Const.CONSTANT_Class:
    108                final int nameIndex = ((org.apache.bcel.classfile.ConstantClass) c).getNameIndex();
    109                c = cpg.getConstantPool().getConstant(nameIndex);
    110                return new ObjectType(((org.apache.bcel.classfile.ConstantUtf8) c).getBytes());
    111            default: // Never reached
    112                throw new RuntimeException("Unknown or invalid constant type at " + super.getIndex());
    113        }
    114    }
    115
    116
    117    @Override
    118    public Type getType( final ConstantPoolGen cpg ) {
    119        switch (cpg.getConstantPool().getConstant(super.getIndex()).getTag()) {
    120            case org.apache.bcel.Const.CONSTANT_String:
    121                return Type.STRING;
    122            case org.apache.bcel.Const.CONSTANT_Float:
    123                return Type.FLOAT;
    124            case org.apache.bcel.Const.CONSTANT_Integer:
    125                return Type.INT;
    126            case org.apache.bcel.Const.CONSTANT_Class:
    127                return Type.CLASS;
    128            default: // Never reached
    129                throw new RuntimeException("Unknown or invalid constant type at " + super.getIndex());
    130        }
    131    }
    132
    133
    134    @Override
    135    public Class<?>[] getExceptions() {
    136        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_STRING_RESOLUTION);
    137    }
    138
    139
    140    /**
    141     * Call corresponding visitor method(s). The order is:
    142     * Call visitor methods of implemented interfaces first, then
    143     * call methods according to the class hierarchy in descending order,
    144     * i.e., the most specific visitXXX() call comes last.
    145     *
    146     * @param v Visitor object
    147     */
    148    @Override
    149    public void accept( final Visitor v ) {
    150        v.visitStackProducer(this);
    151        v.visitPushInstruction(this);
    152        v.visitExceptionThrower(this);
    153        v.visitTypedInstruction(this);
    154        v.visitCPInstruction(this);
    155        v.visitLDC(this);
    156    }
    157}