    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 */
    017package org.apache.bcel.generic;
    018
    019import java.io.DataOutputStream;
    020import java.io.IOException;
    021
    022import org.apache.bcel.ExceptionConst;
    023import org.apache.bcel.util.ByteSequence;
    024
    025/**
    026 * LDC - Push item from constant pool.
    027 *
    028 * <PRE>
    029 * Stack: ... -&gt; ..., item
    030 * </PRE>
    031 */
    032public class LDC extends CPInstruction implements PushInstruction, ExceptionThrower {
    033
    034    /**
    035     * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
    036     */
    037    LDC() {
    038    }
    039
    040    public LDC(final int index) {
    041        super(org.apache.bcel.Const.LDC_W, index);
    042        setSize();
    043    }
    044
    045    /**
    046     * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
    047     * methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last.
    048     *
    049     * @param v Visitor object
    050     */
    051    @Override
    052    public void accept(final Visitor v) {
    053        v.visitStackProducer(this);
    054        v.visitPushInstruction(this);
    055        v.visitExceptionThrower(this);
    056        v.visitTypedInstruction(this);
    057        v.visitCPInstruction(this);
    058        v.visitLDC(this);
    059    }
    060
    061    /**
    062     * Dump instruction as byte code to stream out.
    063     *
    064     * @param out Output stream
    065     */
    066    @Override
    067    public void dump(final DataOutputStream out) throws IOException {
    068        out.writeByte(super.getOpcode());
    069        if (super.getLength() == 2) { // TODO useless check?
    070            out.writeByte(super.getIndex());
    071        } else {
    072            out.writeShort(super.getIndex());
    073        }
    074    }
    075
    076    @Override
    077    public Class<?>[] getExceptions() {
    078        return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_STRING_RESOLUTION);
    079    }
    080
    081    @Override
    082    public Type getType(final ConstantPoolGen cpg) {
    083        switch (cpg.getConstantPool().getConstant(super.getIndex()).getTag()) {
    084        case org.apache.bcel.Const.CONSTANT_String:
    085            return Type.STRING;
    086        case org.apache.bcel.Const.CONSTANT_Float:
    087            return Type.FLOAT;
    088        case org.apache.bcel.Const.CONSTANT_Integer:
    089            return Type.INT;
    090        case org.apache.bcel.Const.CONSTANT_Class:
    091            return Type.CLASS;
    092        default: // Never reached
    093            throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex());
    094        }
    095    }
    096
    097    public Object getValue(final ConstantPoolGen cpg) {
    098        org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(super.getIndex());
    099        switch (c.getTag()) {
    100        case org.apache.bcel.Const.CONSTANT_String:
    101            final int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex();
    102            c = cpg.getConstantPool().getConstant(i);
    103            return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
    104        case org.apache.bcel.Const.CONSTANT_Float:
    105            return Float.valueOf(((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
    106        case org.apache.bcel.Const.CONSTANT_Integer:
    107            return Integer.valueOf(((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
    108        case org.apache.bcel.Const.CONSTANT_Class:
    109            final int nameIndex = ((org.apache.bcel.classfile.ConstantClass) c).getNameIndex();
    110            c = cpg.getConstantPool().getConstant(nameIndex);
    111            return new ObjectType(((org.apache.bcel.classfile.ConstantUtf8) c).getBytes());
    112        default: // Never reached
    113            throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex());
    114        }
    115    }
    116
    117    /**
    118     * Read needed data (e.g. index) from file.
    119     */
    120    @Override
    121    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
    122        super.setLength(2);
    123        super.setIndex(bytes.readUnsignedByte());
    124    }
    125
    126    /**
    127     * Set the index to constant pool and adjust size.
    128     */
    129    @Override
    130    public final void setIndex(final int index) {
    131        super.setIndex(index);
    132        setSize();
    133    }
    134
    135    // Adjust to proper size
    136    protected final void setSize() {
    137        if (super.getIndex() <= org.apache.bcel.Const.MAX_BYTE) { // Fits in one byte?
    138            super.setOpcode(org.apache.bcel.Const.LDC);
    139            super.setLength(2);
    140        } else {
    141            super.setOpcode(org.apache.bcel.Const.LDC_W);
    142            super.setLength(3);
    143        }
    144    }
    145}