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