1 package org.apache.bcel.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
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
57 import java.util.ArrayList;
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 org.apache.bcel.verifier.Verifier
83 * @see #verify()
84 */
85 public abstract class PassVerifier{
86
87 /*** The (warning) messages. */
88 private ArrayList messages = new ArrayList(); //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 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[] getMessages(){
136 verify(); // create messages if not already done (cached!)
137 String[] ret = new String[messages.size()];
138 for (int i=0; i<messages.size(); i++){
139 ret[i] = (String) messages.get(i);
140 }
141 return ret;
142 }
143 }
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