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


1 package com.sun.org.apache.bcel.internal.verifier;
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,
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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
57 import java.util.ArrayList JavaDoc;
58
59 /**
60  * A PassVerifier actually verifies a class file; it is instantiated
61  * by a Verifier.
62  * The verification should conform with a certain pass as described
63  * in The Java Virtual Machine Specification, 2nd edition.
64  * This book describes four passes. Pass one means loading the
65  * class and verifying a few static constraints. Pass two actually
66  * verifies some other constraints that could enforce loading in
67  * referenced class files. Pass three is the first pass that actually
68  * checks constraints in the code array of a method in the class file;
69  * it has two parts with the first verifying static constraints and
70  * the second part verifying structural constraints (where a data flow
71  * analysis is used for). The fourth pass, finally, performs checks
72  * that can only be done at run-time.
73  * JustIce does not have a run-time pass, but certain constraints that
74  * are usually delayed until run-time for performance reasons are also
75  * checked during the second part of pass three.
76  * PassVerifier instances perform caching.
77  * That means, if you really want a new verification run of a certain
78  * pass you must use a new instance of a given PassVerifier.
79  *
80  * @version $Id: PassVerifier.java,v 1.1.1.1 2001/10/29 20:00:31 jvanzyl Exp $
81  * @author <A HREF="http://www.inf.fu-berlin.de/~ehaase"/>Enver Haase</A>
82  * @see com.sun.org.apache.bcel.internal.verifier.Verifier
83  * @see #verify()
84  */

85 public abstract class PassVerifier{
86
87     /** The (warning) messages. */
88     private ArrayList JavaDoc messages = new ArrayList JavaDoc(); //Type of elements: String
89

90     /** The VerificationResult cache. */
91     private VerificationResult verificationResult = null;
92
93     /**
94      * This method runs a verification pass conforming to the
95      * Java Virtual Machine Specification, 2nd edition, on a
96      * class file.
97      * PassVerifier instances perform caching;
98      * i.e. if the verify() method once determined a VerificationResult,
99      * then this result may be returned after every invocation of this
100      * method instead of running the verification pass anew; likewise with
101      * the result of getMessages().
102      *
103      * @see #getMessages()
104      * @see #addMessage(String)
105      */

106     public VerificationResult verify(){
107         if (verificationResult == null){
108             verificationResult = do_verify();
109         }
110         return verificationResult;
111     }
112
113     /** Does the real verification work, uncached. */
114     public abstract VerificationResult do_verify();
115
116     /**
117      * This method adds a (warning) message to the message pool of this
118      * PassVerifier. This method is normally only internally used by
119      * BCEL's class file verifier "JustIce" and should not be used from
120      * the outside.
121      *
122      * @see #getMessages()
123      */

124     public void addMessage(String JavaDoc message){
125         messages.add(message);
126     }
127
128     /**
129      * Returns the (warning) messages that this PassVerifier accumulated
130      * during its do_verify()ing work.
131      *
132      * @see #addMessage(String)
133      * @see #do_verify()
134      */

135     public String JavaDoc[] getMessages(){
136         verify(); // create messages if not already done (cached!)
137
String JavaDoc[] ret = new String JavaDoc[messages.size()];
138         for (int i=0; i<messages.size(); i++){
139             ret[i] = (String JavaDoc) messages.get(i);
140         }
141         return ret;
142     }
143 }
144
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