1 /*
2  * Licensed to the Apache Software Foundation (ASF) under one or more
3  * contributor license agreements.  See the NOTICE file distributed with
4  * this work for additional information regarding copyright ownership.
5  * The ASF licenses this file to You under the Apache License, Version 2.0
6  * (the "License"); you may not use this file except in compliance with
7  * the License.  You may obtain a copy of the License at
8  *
9  *      http://www.apache.org/licenses/LICENSE-2.0
10  *
11  *  Unless required by applicable law or agreed to in writing, software
12  *  distributed under the License is distributed on an "AS IS" BASIS,
13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  *  See the License for the specific language governing permissions and
15  *  limitations under the License.
16  *
17  */
18 package org.apache.bcel.generic;
19 
20 import java.io.DataOutputStream;
21 import java.io.IOException;
22 
23 import org.apache.bcel.ExceptionConst;
24 import org.apache.bcel.util.ByteSequence;
25 
26 /**
27  * LDC - Push item from constant pool.
28  *
29  * <PRE>Stack: ... -&gt; ..., item</PRE>
30  *
31  * @version $Id$
32  */
33 public class LDC extends CPInstruction implements PushInstruction, ExceptionThrower {
34 
35     /**
36      * Empty constructor needed for Instruction.readInstruction.
37      * Not to be used otherwise.
38      */
LDC()39     LDC() {
40     }
41 
42 
LDC(final int index)43     public LDC(final int index) {
44         super(org.apache.bcel.Const.LDC_W, index);
45         setSize();
46     }
47 
48 
49     // Adjust to proper size
setSize()50     protected final void setSize() {
51         if (super.getIndex() <= org.apache.bcel.Const.MAX_BYTE) { // Fits in one byte?
52             super.setOpcode(org.apache.bcel.Const.LDC);
53             super.setLength(2);
54         } else {
55             super.setOpcode(org.apache.bcel.Const.LDC_W);
56             super.setLength(3);
57         }
58     }
59 
60 
61     /**
62      * Dump instruction as byte code to stream out.
63      * @param out Output stream
64      */
65     @Override
dump( final DataOutputStream out )66     public void dump( final DataOutputStream out ) throws IOException {
67         out.writeByte(super.getOpcode());
68         if (super.getLength() == 2) { // TODO useless check?
69             out.writeByte(super.getIndex());
70         } else {
71             out.writeShort(super.getIndex());
72         }
73     }
74 
75 
76     /**
77      * Set the index to constant pool and adjust size.
78      */
79     @Override
setIndex( final int index )80     public final void setIndex( final int index ) {
81         super.setIndex(index);
82         setSize();
83     }
84 
85 
86     /**
87      * Read needed data (e.g. index) from file.
88      */
89     @Override
initFromFile( final ByteSequence bytes, final boolean wide )90     protected void initFromFile( final ByteSequence bytes, final boolean wide ) throws IOException {
91         super.setLength(2);
92         super.setIndex(bytes.readUnsignedByte());
93     }
94 
95 
getValue( final ConstantPoolGen cpg )96     public Object getValue( final ConstantPoolGen cpg ) {
97         org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(super.getIndex());
98         switch (c.getTag()) {
99             case org.apache.bcel.Const.CONSTANT_String:
100                 final int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex();
101                 c = cpg.getConstantPool().getConstant(i);
102                 return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
103             case org.apache.bcel.Const.CONSTANT_Float:
104                 return new Float(((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
105             case org.apache.bcel.Const.CONSTANT_Integer:
106                 return Integer.valueOf(((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
107             case org.apache.bcel.Const.CONSTANT_Class:
108                 final int nameIndex = ((org.apache.bcel.classfile.ConstantClass) c).getNameIndex();
109                 c = cpg.getConstantPool().getConstant(nameIndex);
110                 return new ObjectType(((org.apache.bcel.classfile.ConstantUtf8) c).getBytes());
111             default: // Never reached
112                 throw new RuntimeException("Unknown or invalid constant type at " + super.getIndex());
113         }
114     }
115 
116 
117     @Override
getType( final ConstantPoolGen cpg )118     public Type getType( final ConstantPoolGen cpg ) {
119         switch (cpg.getConstantPool().getConstant(super.getIndex()).getTag()) {
120             case org.apache.bcel.Const.CONSTANT_String:
121                 return Type.STRING;
122             case org.apache.bcel.Const.CONSTANT_Float:
123                 return Type.FLOAT;
124             case org.apache.bcel.Const.CONSTANT_Integer:
125                 return Type.INT;
126             case org.apache.bcel.Const.CONSTANT_Class:
127                 return Type.CLASS;
128             default: // Never reached
129                 throw new RuntimeException("Unknown or invalid constant type at " + super.getIndex());
130         }
131     }
132 
133 
134     @Override
getExceptions()135     public Class<?>[] getExceptions() {
136         return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_STRING_RESOLUTION);
137     }
138 
139 
140     /**
141      * Call corresponding visitor method(s). The order is:
142      * Call visitor methods of implemented interfaces first, then
143      * call methods according to the class hierarchy in descending order,
144      * i.e., the most specific visitXXX() call comes last.
145      *
146      * @param v Visitor object
147      */
148     @Override
accept( final Visitor v )149     public void accept( final Visitor v ) {
150         v.visitStackProducer(this);
151         v.visitPushInstruction(this);
152         v.visitExceptionThrower(this);
153         v.visitTypedInstruction(this);
154         v.visitCPInstruction(this);
155         v.visitLDC(this);
156     }
157 }
158