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    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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