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}