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
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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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