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


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.classfile.Constant;
22 import org.apache.bcel.classfile.ConstantClass;
23 import org.apache.bcel.classfile.ConstantPool;
24 import org.apache.bcel.util.ByteSequence;
25
26 /**
27  * Abstract super class for instructions that use an index into the
28  * constant pool such as LDC, INVOKEVIRTUAL, etc.
29  *
30  * @see ConstantPoolGen
31  * @see LDC
32  * @see INVOKEVIRTUAL
33  *
34  * @version $Id: CPInstruction.java 386056 2006-03-15 11:31:56Z tcurdt $
35  * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
36  */
37 public abstract class CPInstruction extends Instruction implements TypedInstruction,
38         IndexedInstruction {
39
40     protected int index; // index to constant pool
41
42
43     /**
44      * Empty constructor needed for the Class.newInstance() statement in
45      * Instruction.readInstruction(). Not to be used otherwise.
46      */
47     CPInstruction() {
48     }
49
50
51     /**
52      * @param index to constant pool
53      */
54     protected CPInstruction(short opcode, int index) {
55         super(opcode, (short) 3);
56         setIndex(index);
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         out.writeShort(index);
67     }
68
69
70     /**
71      * Long output format:
72      *
73      * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]"
74      * "("&lt;length of instruction&gt;")" "&lt;"&lt; constant pool index&gt;"&gt;"
75      *
76      * @param verbose long/short format switch
77      * @return mnemonic for instruction
78      */
79     public String JavaDoc toString( boolean verbose ) {
80         return super.toString(verbose) + " " + index;
81     }
82
83
84     /**
85      * @return mnemonic for instruction with symbolic references resolved
86      */
87     public String JavaDoc toString( ConstantPool cp ) {
88         Constant c = cp.getConstant(index);
89         String JavaDoc str = cp.constantToString(c);
90         if (c instanceof ConstantClass) {
91             str = str.replace('.', '/');
92         }
93         return org.apache.bcel.Constants.OPCODE_NAMES[opcode] + " " + str;
94     }
95
96
97     /**
98      * Read needed data (i.e., index) from file.
99      * @param bytes input stream
100      * @param wide wide prefix?
101      */
102     protected void initFromFile( ByteSequence bytes, boolean wide ) throws IOException JavaDoc {
103         setIndex(bytes.readUnsignedShort());
104         length = 3;
105     }
106
107
108     /**
109      * @return index in constant pool referred by this instruction.
110      */
111     public final int getIndex() {
112         return index;
113     }
114
115
116     /**
117      * Set the index to constant pool.
118      * @param index in constant pool.
119      */
120     public void setIndex( int index ) {
121         if (index < 0) {
122             throw new ClassGenException("Negative index value: " + index);
123         }
124         this.index = index;
125     }
126
127
128     /** @return type related with this instruction.
129      */
130     public Type getType( ConstantPoolGen cpg ) {
131         ConstantPool cp = cpg.getConstantPool();
132         String JavaDoc name = cp.getConstantString(index, org.apache.bcel.Constants.CONSTANT_Class);
133         if (!name.startsWith("[")) {
134             name = "L" + name + ";";
135         }
136         return Type.getType(name);
137     }
138 }
139
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