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Java > Open Source Codes > org > apache > bcel > generic > LDC


1 /*
2  * Copyright 2000-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 package org.apache.bcel.generic;
18
19 import java.io.DataOutputStream JavaDoc;
20 import java.io.IOException JavaDoc;
21 import org.apache.bcel.util.ByteSequence;
22
23 /**
24  * LDC - Push item from constant pool.
25  *
26  * <PRE>Stack: ... -&gt; ..., item</PRE>
27  *
28  * @version $Id: LDC.java 386056 2006-03-15 11:31:56Z tcurdt $
29  * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
30  */
31 public class LDC extends CPInstruction implements PushInstruction, ExceptionThrower,
32         TypedInstruction {
33
34     /**
35      * Empty constructor needed for the Class.newInstance() statement in
36      * Instruction.readInstruction(). Not to be used otherwise.
37      */
38     LDC() {
39     }
40
41
42     public LDC(int index) {
43         super(org.apache.bcel.Constants.LDC_W, index);
44         setSize();
45     }
46
47
48     // Adjust to proper size
49 protected final void setSize() {
50         if (index <= org.apache.bcel.Constants.MAX_BYTE) { // Fits in one byte?
51 opcode = org.apache.bcel.Constants.LDC;
52             length = 2;
53         } else {
54             opcode = org.apache.bcel.Constants.LDC_W;
55             length = 3;
56         }
57     }
58
59
60     /**
61      * Dump instruction as byte code to stream out.
62      * @param out Output stream
63      */
64     public void dump( DataOutputStream JavaDoc out ) throws IOException JavaDoc {
65         out.writeByte(opcode);
66         if (length == 2) {
67             out.writeByte(index);
68         } else {
69             out.writeShort(index);
70         }
71     }
72
73
74     /**
75      * Set the index to constant pool and adjust size.
76      */
77     public final void setIndex( int index ) {
78         super.setIndex(index);
79         setSize();
80     }
81
82
83     /**
84      * Read needed data (e.g. index) from file.
85      */
86     protected void initFromFile( ByteSequence bytes, boolean wide ) throws IOException JavaDoc {
87         length = 2;
88         index = bytes.readUnsignedByte();
89     }
90
91
92     public Object JavaDoc getValue( ConstantPoolGen cpg ) {
93         org.apache.bcel.classfile.Constant c = cpg.getConstantPool().getConstant(index);
94         switch (c.getTag()) {
95             case org.apache.bcel.Constants.CONSTANT_String:
96                 int i = ((org.apache.bcel.classfile.ConstantString) c).getStringIndex();
97                 c = cpg.getConstantPool().getConstant(i);
98                 return ((org.apache.bcel.classfile.ConstantUtf8) c).getBytes();
99             case org.apache.bcel.Constants.CONSTANT_Float:
100                 return new Float JavaDoc(((org.apache.bcel.classfile.ConstantFloat) c).getBytes());
101             case org.apache.bcel.Constants.CONSTANT_Integer:
102                 return new Integer JavaDoc(((org.apache.bcel.classfile.ConstantInteger) c).getBytes());
103             case org.apache.bcel.Constants.CONSTANT_Class:
104                 return c;
105             default: // Never reached
106 throw new RuntimeException JavaDoc("Unknown or invalid constant type at " + index);
107         }
108     }
109
110
111     public Type getType( ConstantPoolGen cpg ) {
112         switch (cpg.getConstantPool().getConstant(index).getTag()) {
113             case org.apache.bcel.Constants.CONSTANT_String:
114                 return Type.STRING;
115             case org.apache.bcel.Constants.CONSTANT_Float:
116                 return Type.FLOAT;
117             case org.apache.bcel.Constants.CONSTANT_Integer:
118                 return Type.INT;
119             case org.apache.bcel.Constants.CONSTANT_Class:
120                 return Type.CLASS;
121             default: // Never reached
122 throw new RuntimeException JavaDoc("Unknown or invalid constant type at " + index);
123         }
124     }
125
126
127     public Class JavaDoc[] getExceptions() {
128         return org.apache.bcel.ExceptionConstants.EXCS_STRING_RESOLUTION;
129     }
130
131
132     /**
133      * Call corresponding visitor method(s). The order is:
134      * Call visitor methods of implemented interfaces first, then
135      * call methods according to the class hierarchy in descending order,
136      * i.e., the most specific visitXXX() call comes last.
137      *
138      * @param v Visitor object
139      */
140     public void accept( Visitor v ) {
141         v.visitStackProducer(this);
142         v.visitPushInstruction(this);
143         v.visitExceptionThrower(this);
144         v.visitTypedInstruction(this);
145         v.visitCPInstruction(this);
146         v.visitLDC(this);
147     }
148 }
149
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