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Java > Open Source Codes > com > sun > org > apache > bcel > internal > generic > LocalVariableInstruction


1 package com.sun.org.apache.bcel.internal.generic;
2
3 /* ====================================================================
4  * The Apache Software License, Version 1.1
5  *
6  * Copyright (c) 2001 The Apache Software Foundation. All rights
7  * reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright
14  * notice, this list of conditions and the following disclaimer.
15  *
16  * 2. Redistributions in binary form must reproduce the above copyright
17  * notice, this list of conditions and the following disclaimer in
18  * the documentation and/or other materials provided with the
19  * distribution.
20  *
21  * 3. The end-user documentation included with the redistribution,
22  * if any, must include the following acknowledgment:
23  * "This product includes software developed by the
24  * Apache Software Foundation (http://www.apache.org/)."
25  * Alternately, this acknowledgment may appear in the software itself,
26  * if and wherever such third-party acknowledgments normally appear.
27  *
28  * 4. The names "Apache" and "Apache Software Foundation" and
29  * "Apache BCEL" must not be used to endorse or promote products
30  * derived from this software without prior written permission. For
31  * written permission, please contact apache@apache.org.
32  *
33  * 5. Products derived from this software may not be called "Apache",
34  * "Apache BCEL", nor may "Apache" appear in their name, without
35  * prior written permission of the Apache Software Foundation.
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37  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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41  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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43  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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45  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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51  * This software consists of voluntary contributions made by many
52  * individuals on behalf of the Apache Software Foundation. For more
53  * information on the Apache Software Foundation, please see
54  * <http://www.apache.org/>.
55  */
56 import java.io.*;
57 import com.sun.org.apache.bcel.internal.util.ByteSequence;
58 import com.sun.org.apache.bcel.internal.classfile.Utility;
59 import com.sun.org.apache.bcel.internal.Constants;
60
61 /**
62  * Abstract super class for instructions dealing with local variables.
63  *
64  * @version $Id: LocalVariableInstruction.java,v 1.1.1.1 2001/10/29 20:00:23 jvanzyl Exp $
65  * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
66  */
67 public abstract class LocalVariableInstruction extends Instruction
68   implements TypedInstruction, IndexedInstruction {
69   protected int n = -1; // index of referenced variable
70 private short c_tag = -1; // compact version, such as ILOAD_0
71 private short canon_tag = -1; // canonical tag such as ILOAD
72
73   private final boolean wide() { return n > Constants.MAX_BYTE; }
74
75   /**
76    * Empty constructor needed for the Class.newInstance() statement in
77    * Instruction.readInstruction(). Not to be used otherwise.
78    * tag and length are defined in readInstruction and initFromFile, respectively.
79    */
80   LocalVariableInstruction(short canon_tag, short c_tag) {
81     super();
82     this.canon_tag = canon_tag;
83     this.c_tag = c_tag;
84   }
85
86   /**
87    * Empty constructor needed for the Class.newInstance() statement in
88    * Instruction.readInstruction(). Also used by IINC()!
89    */
90   LocalVariableInstruction() {
91   }
92
93   /**
94    * @param opcode Instruction opcode
95    * @param c_tag Instruction number for compact version, ALOAD_0, e.g.
96    * @param n local variable index (unsigned short)
97    */
98   protected LocalVariableInstruction(short opcode, short c_tag, int n) {
99     super(opcode, (short)2);
100
101     this.c_tag = c_tag;
102     canon_tag = opcode;
103
104     setIndex(n);
105   }
106
107   /**
108    * Dump instruction as byte code to stream out.
109    * @param out Output stream
110    */
111   public void dump(DataOutputStream out) throws IOException {
112     if(wide()) // Need WIDE prefix ?
113 out.writeByte(Constants.WIDE);
114
115     out.writeByte(opcode);
116
117     if(length > 1) { // Otherwise ILOAD_n, instruction, e.g.
118 if(wide())
119     out.writeShort(n);
120       else
121     out.writeByte(n);
122     }
123   }
124
125   /**
126    * Long output format:
127    *
128    * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]"
129    * "("&lt;length of instruction&gt;")" "&lt;"&lt; local variable index&gt;"&gt;"
130    *
131    * @param verbose long/short format switch
132    * @return mnemonic for instruction
133    */
134   public String JavaDoc toString(boolean verbose) {
135     if(((opcode >= Constants.ILOAD_0) &&
136     (opcode <= Constants.ALOAD_3)) ||
137        ((opcode >= Constants.ISTORE_0) &&
138     (opcode <= Constants.ASTORE_3)))
139       return super.toString(verbose);
140     else
141       return super.toString(verbose) + " " + n;
142   }
143
144   /**
145    * Read needed data (e.g. index) from file.
146    * PRE: (ILOAD <= tag <= ALOAD_3) || (ISTORE <= tag <= ASTORE_3)
147    */
148   protected void initFromFile(ByteSequence bytes, boolean wide)
149     throws IOException
150   {
151     if(wide) {
152       n = bytes.readUnsignedShort();
153       length = 4;
154     } else if(((opcode >= Constants.ILOAD) &&
155            (opcode <= Constants.ALOAD)) ||
156           ((opcode >= Constants.ISTORE) &&
157            (opcode <= Constants.ASTORE))) {
158       n = bytes.readUnsignedByte();
159       length = 2;
160     } else if(opcode <= Constants.ALOAD_3) { // compact load instruction such as ILOAD_2
161 n = (opcode - Constants.ILOAD_0) % 4;
162       length = 1;
163     } else { // Assert ISTORE_0 <= tag <= ASTORE_3
164 n = (opcode - Constants.ISTORE_0) % 4;
165       length = 1;
166     }
167  }
168
169   /**
170    * @return local variable index referred by this instruction.
171    */
172   public final int getIndex() { return n; }
173
174   /**
175    * Set the local variable index
176    */
177   public void setIndex(int n) {
178     if((n < 0) || (n > Constants.MAX_SHORT))
179       throw new ClassGenException("Illegal value: " + n);
180
181     this.n = n;
182
183     if(n >= 0 && n <= 3) { // Use more compact instruction xLOAD_n
184 opcode = (short)(c_tag + n);
185       length = 1;
186     } else {
187       opcode = canon_tag;
188       
189       if(wide()) // Need WIDE prefix ?
190 length = 4;
191       else
192     length = 2;
193     }
194   }
195
196   /** @return canonical tag for instruction, e.g., ALOAD for ALOAD_0
197    */
198   public short getCanonicalTag() {
199     return canon_tag;
200   }
201
202   /**
203    * Returns the type associated with the instruction -
204    * in case of ALOAD or ASTORE Type.OBJECT is returned.
205    * This is just a bit incorrect, because ALOAD and ASTORE
206    * may work on every ReferenceType (including Type.NULL) and
207    * ASTORE may even work on a ReturnaddressType .
208    * @return type associated with the instruction
209    */
210   public Type getType(ConstantPoolGen cp) {
211     switch(canon_tag) {
212     case Constants.ILOAD: case Constants.ISTORE:
213       return Type.INT;
214     case Constants.LLOAD: case Constants.LSTORE:
215       return Type.LONG;
216     case Constants.DLOAD: case Constants.DSTORE:
217       return Type.DOUBLE;
218     case Constants.FLOAD: case Constants.FSTORE:
219       return Type.FLOAT;
220     case Constants.ALOAD: case Constants.ASTORE:
221       return Type.OBJECT;
222
223     default: throw new ClassGenException("Oops: unknown case in switch" + canon_tag);
224     }
225   }
226 }
227
228
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