001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.bcel.generic;
020
021import java.io.DataOutputStream;
022import java.io.IOException;
023
024import org.apache.bcel.ExceptionConst;
025import org.apache.bcel.util.ByteSequence;
026
027/**
028 * LDC - Push item from constant pool.
029 *
030 * <PRE>
031 * Stack: ... -&gt; ..., item
032 * </PRE>
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        case org.apache.bcel.Const.CONSTANT_Dynamic:
095            return Type.OBJECT;
096        default: // Never reached
097            throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex());
098        }
099    }
100
101    public Object getValue(final ConstantPoolGen cpg) {
102        org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(super.getIndex());
103        switch (c.getTag()) {
104        case org.apache.bcel.Const.CONSTANT_String:
105            final int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex();
106            c = cpg.getConstantPool().getConstant(i);
107            return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
108        case org.apache.bcel.Const.CONSTANT_Float:
109            return Float.valueOf(((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
110        case org.apache.bcel.Const.CONSTANT_Integer:
111            return Integer.valueOf(((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
112        case org.apache.bcel.Const.CONSTANT_Class:
113            final int nameIndex = ((org.apache.bcel.classfile.ConstantClass) c).getNameIndex();
114            c = cpg.getConstantPool().getConstant(nameIndex);
115            return Type.getType(Type.internalTypeNameToSignature(((org.apache.bcel.classfile.ConstantUtf8) c).getBytes()));
116        case org.apache.bcel.Const.CONSTANT_Dynamic:
117            // Really not sure what to return here, maybe a BootstrapMethod instance but how do we get it?
118            return c;
119        default: // Never reached
120            throw new IllegalArgumentException("Unknown or invalid constant type at " + super.getIndex());
121        }
122    }
123
124    /**
125     * Reads needed data (for example index) from file.
126     */
127    @Override
128    protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
129        super.setLength(2);
130        super.setIndex(bytes.readUnsignedByte());
131    }
132
133    /**
134     * Sets the index to constant pool and adjust size.
135     */
136    @Override
137    public final void setIndex(final int index) {
138        super.setIndex(index);
139        setSize();
140    }
141
142    // Adjust to proper size
143    protected final void setSize() {
144        if (super.getIndex() <= org.apache.bcel.Const.MAX_BYTE) { // Fits in one byte?
145            super.setOpcode(org.apache.bcel.Const.LDC);
146            super.setLength(2);
147        } else {
148            super.setOpcode(org.apache.bcel.Const.LDC_W);
149            super.setLength(3);
150        }
151    }
152}