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Java > Open Source Codes > com > sun > org > apache > bcel > internal > verifier > structurals > LocalVariables


1 package com.sun.org.apache.bcel.internal.verifier.structurals;
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
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53  * information on the Apache Software Foundation, please see
54  * <http://www.apache.org/>.
55  */
56
57 import com.sun.org.apache.bcel.internal.generic.Type;
58 import com.sun.org.apache.bcel.internal.generic.ReferenceType;
59 import com.sun.org.apache.bcel.internal.verifier.exc.*;
60
61 /**
62  * This class implements an array of local variables used for symbolic JVM
63  * simulation.
64  *
65  * @version $Id: LocalVariables.java,v 1.1.1.1 2001/10/29 20:00:41 jvanzyl Exp $
66  * @author <A HREF="http://www.inf.fu-berlin.de/~ehaase"/>Enver Haase</A>
67  */
68 public class LocalVariables{
69     /** The Type[] containing the local variable slots. */
70     private Type[] locals;
71
72     /**
73      * Creates a new LocalVariables object.
74      */
75     public LocalVariables(int maxLocals){
76         locals = new Type[maxLocals];
77         for (int i=0; i<maxLocals; i++){
78             locals[i] = Type.UNKNOWN;
79         }
80     }
81
82     /**
83      * Returns a deep copy of this object; i.e. the clone
84      * operates on a new local variable array.
85      * However, the Type objects in the array are shared.
86      */
87     protected Object JavaDoc clone(){
88         LocalVariables lvs = new LocalVariables(locals.length);
89         for (int i=0; i<locals.length; i++){
90             lvs.locals[i] = this.locals[i];
91         }
92         return lvs;
93     }
94
95     /**
96      * Returns the type of the local variable slot i.
97      */
98     public Type get(int i){
99         return locals[i];
100     }
101
102     /**
103      * Returns a (correctly typed) clone of this object.
104      * This is equivalent to ((LocalVariables) this.clone()).
105      */
106     public LocalVariables getClone(){
107         return (LocalVariables) this.clone();
108     }
109
110     /**
111      * Returns the number of local variable slots this
112      * LocalVariables instance has.
113      */
114     public int maxLocals(){
115         return locals.length;
116     }
117
118     /**
119      * Sets a new Type for the given local variable slot.
120      */
121     public void set(int i, Type type){
122         if (type == Type.BYTE || type == Type.SHORT || type == Type.BOOLEAN || type == Type.CHAR){
123             throw new AssertionViolatedException("LocalVariables do not know about '"+type+"'. Use Type.INT instead.");
124         }
125         locals[i] = type;
126     }
127
128     /*
129      * Fulfills the general contract of Object.equals().
130      */
131     public boolean equals(Object JavaDoc o){
132         if (!(o instanceof LocalVariables)) return false;
133         LocalVariables lv = (LocalVariables) o;
134         if (this.locals.length != lv.locals.length) return false;
135         for (int i=0; i<this.locals.length; i++){
136             if (!this.locals[i].equals(lv.locals[i])){
137                 //System.out.println(this.locals[i]+" is not "+lv.locals[i]);
138 return false;
139             }
140         }
141         return true;
142     }
143     
144     /**
145      * Merges two local variables sets as described in the Java Virtual Machine Specification,
146      * Second Edition, section 4.9.2, page 146.
147      */
148     public void merge(LocalVariables lv){
149
150         if (this.locals.length != lv.locals.length){
151             throw new AssertionViolatedException("Merging LocalVariables of different size?!? From different methods or what?!?");
152         }
153
154         for (int i=0; i<locals.length; i++){
155             merge(lv, i);
156         }
157     }
158     
159     /**
160      * Merges a single local variable.
161      *
162      * @see #merge(LocalVariables)
163      */
164     private void merge(LocalVariables lv, int i){
165         
166         // We won't accept an unitialized object if we know it was initialized;
167 // compare vmspec2, 4.9.4, last paragraph.
168 if ( (!(locals[i] instanceof UninitializedObjectType)) && (lv.locals[i] instanceof UninitializedObjectType) ){
169             throw new StructuralCodeConstraintException("Backwards branch with an uninitialized object in the local variables detected.");
170         }
171         // Even harder, what about _different_ uninitialized object types?!
172 if ( (!(locals[i].equals(lv.locals[i]))) && (locals[i] instanceof UninitializedObjectType) && (lv.locals[i] instanceof UninitializedObjectType) ){
173             throw new StructuralCodeConstraintException("Backwards branch with an uninitialized object in the local variables detected.");
174         }
175         // If we just didn't know that it was initialized, we have now learned.
176 if (locals[i] instanceof UninitializedObjectType){
177             if (! (lv.locals[i] instanceof UninitializedObjectType)){
178                 locals[i] = ((UninitializedObjectType) locals[i]).getInitialized();
179             }
180         }
181         if ((locals[i] instanceof ReferenceType) && (lv.locals[i] instanceof ReferenceType)){
182             if (! locals[i].equals(lv.locals[i])){ // needed in case of two UninitializedObjectType instances
183 Type sup = ((ReferenceType) locals[i]).firstCommonSuperclass((ReferenceType) (lv.locals[i]));
184
185                 if (sup != null){
186                     locals[i] = sup;
187                 }
188                 else{
189                     // We should have checked this in Pass2!
190 throw new AssertionViolatedException("Could not load all the super classes of '"+locals[i]+"' and '"+lv.locals[i]+"'.");
191                 }
192             }
193         }
194         else{
195             if (! (locals[i].equals(lv.locals[i])) ){
196 /*TODO
197                 if ((locals[i] instanceof com.sun.org.apache.bcel.internal.generic.ReturnaddressType) && (lv.locals[i] instanceof com.sun.org.apache.bcel.internal.generic.ReturnaddressType)){
198                     //System.err.println("merging "+locals[i]+" and "+lv.locals[i]);
199                     throw new AssertionViolatedException("Merging different ReturnAddresses: '"+locals[i]+"' and '"+lv.locals[i]+"'.");
200                 }
201 */
202                 locals[i] = Type.UNKNOWN;
203             }
204         }
205     }
206
207     /**
208      * Returns a String representation of this object.
209      */
210     public String JavaDoc toString(){
211         String JavaDoc s = new String JavaDoc();
212         for (int i=0; i<locals.length; i++){
213             s += Integer.toString(i)+": "+locals[i]+"\n";
214         }
215         return s;
216     }
217
218     /**
219      * Replaces all occurences of u in this local variables set
220      * with an "initialized" ObjectType.
221      */
222     public void initializeObject(UninitializedObjectType u){
223         for (int i=0; i<locals.length; i++){
224             if (locals[i] == u){
225                 locals[i] = u.getInitialized();
226             }
227         }
228     }
229 }
230
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