1 package org.apache.bcel.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.
36 *
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
40 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
41 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
42 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
43 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
44 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
45 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
46 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
47 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
48 * SUCH DAMAGE.
49 * ====================================================================
50 *
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 org.apache.bcel.util.ByteSequence;
58 import org.apache.bcel.classfile.Utility;
59 import org.apache.bcel.Constants;
60
61 /***
62 * Abstract super class for instructions dealing with local variables.
63 *
64 * @version $Id: LocalVariableInstruction.java,v 1.2 2002/08/07 18:01:32 mdahm 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 * <name of opcode> "["<opcode number>"]"
129 * "("<length of instruction>")" "<"< local variable index>">"
130 *
131 * @param verbose long/short format switch
132 * @return mnemonic for instruction
133 */
134 public String 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 }
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