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