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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
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package org.apache.bcel.verifier;

import java.util.ArrayList;
import java.util.List;

A PassVerifier actually verifies a class file; it is instantiated
by a Verifier.
The verification should conform with a certain pass as described
in The Java Virtual Machine Specification, 2nd edition.
This book describes four passes. Pass one means loading the
class and verifying a few static constraints. Pass two actually
verifies some other constraints that could enforce loading in
referenced class files. Pass three is the first pass that actually
checks constraints in the code array of a method in the class file;
it has two parts with the first verifying static constraints and
the second part verifying structural constraints (where a data flow
analysis is used for). The fourth pass, finally, performs checks
that can only be done at run-time.
JustIce does not have a run-time pass, but certain constraints that
are usually delayed until run-time for performance reasons are also
checked during the second part of pass three.
PassVerifier instances perform caching.
That means, if you really want a new verification run of a certain
pass you must use a new instance of a given PassVerifier.
See Also:
Verifier
verify()/**
 * A PassVerifier actually verifies a class file; it is instantiated
 * by a Verifier.
 * The verification should conform with a certain pass as described
 * in The Java Virtual Machine Specification, 2nd edition.
 * This book describes four passes. Pass one means loading the
 * class and verifying a few static constraints. Pass two actually
 * verifies some other constraints that could enforce loading in
 * referenced class files. Pass three is the first pass that actually
 * checks constraints in the code array of a method in the class file;
 * it has two parts with the first verifying static constraints and
 * the second part verifying structural constraints (where a data flow
 * analysis is used for). The fourth pass, finally, performs checks
 * that can only be done at run-time.
 * JustIce does not have a run-time pass, but certain constraints that
 * are usually delayed until run-time for performance reasons are also
 * checked during the second part of pass three.
 * PassVerifier instances perform caching.
 * That means, if you really want a new verification run of a certain
 * pass you must use a new instance of a given PassVerifier.
 *
 * @see Verifier
 * @see #verify()
 */
public abstract class PassVerifier {

    
The (warning) messages. /** The (warning) messages. */
    private final List<String> messages = new ArrayList<>();
    
The VerificationResult cache. /** The VerificationResult cache. */
    private VerificationResult verificationResult = null;


    
This method runs a verification pass conforming to the
Java Virtual Machine Specification, 2nd edition, on a
class file.
PassVerifier instances perform caching;
i.e. if the verify() method once determined a VerificationResult,
then this result may be returned after every invocation of this
method instead of running the verification pass anew; likewise with
the result of getMessages().
See Also:
getMessages()
addMessage(String)/**
     * This method runs a verification pass conforming to the
     * Java Virtual Machine Specification, 2nd edition, on a
     * class file.
     * PassVerifier instances perform caching;
     * i.e. if the verify() method once determined a VerificationResult,
     * then this result may be returned after every invocation of this
     * method instead of running the verification pass anew; likewise with
     * the result of getMessages().
     *
     * @see #getMessages()
     * @see #addMessage(String)
     */
    public VerificationResult verify() {
        if (verificationResult == null) {
            verificationResult = do_verify();
        }
        return verificationResult;
    }


    
Does the real verification work, uncached. /** Does the real verification work, uncached. */
    public abstract VerificationResult do_verify();


    
This method adds a (warning) message to the message pool of this
PassVerifier. This method is normally only internally used by
BCEL's class file verifier "JustIce" and should not be used from
the outside.
See Also:
getMessages()/**
     * This method adds a (warning) message to the message pool of this
     * PassVerifier. This method is normally only internally used by
     * BCEL's class file verifier "JustIce" and should not be used from
     * the outside.
     *
     * @see #getMessages()
     */
    public void addMessage( final String message ) {
        messages.add(message);
    }


    
Returns the (warning) messages that this PassVerifier accumulated
during its do_verify()ing work.
See Also:
addMessage(String)
do_verify()/**
     * Returns the (warning) messages that this PassVerifier accumulated
     * during its do_verify()ing work.
     *
     * @see #addMessage(String)
     * @see #do_verify()
     */
    public String[] getMessages() {
        verify(); // create messages if not already done (cached!)
        return messages.toArray(new String[messages.size()]);
    }
}