    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 *  Unless required by applicable law or agreed to in writing, software
    012 *  distributed under the License is distributed on an "AS IS" BASIS,
    013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 *  See the License for the specific language governing permissions and
    015 *  limitations under the License.
    016 */
    017package org.apache.bcel.verifier;
    018
    019import java.util.ArrayList;
    020import java.util.List;
    021
    022import org.apache.commons.lang3.ArrayUtils;
    023
    024/**
    025 * A PassVerifier actually verifies a class file; it is instantiated by a Verifier. The verification should conform with
    026 * a certain pass as described in The Java Virtual Machine Specification, 2nd edition. This book describes four passes.
    027 * Pass one means loading the class and verifying a few static constraints. Pass two actually verifies some other
    028 * constraints that could enforce loading in referenced class files. Pass three is the first pass that actually checks
    029 * constraints in the code array of a method in the class file; it has two parts with the first verifying static
    030 * constraints and the second part verifying structural constraints (where a data flow analysis is used for). The fourth
    031 * pass, finally, performs checks that can only be done at run-time. JustIce does not have a run-time pass, but certain
    032 * constraints that are usually delayed until run-time for performance reasons are also checked during the second part
    033 * of pass three. PassVerifier instances perform caching. That means, if you really want a new verification run of a
    034 * certain pass you must use a new instance of a given PassVerifier.
    035 *
    036 * @see Verifier
    037 * @see #verify()
    038 */
    039public abstract class PassVerifier {
    040
    041    /** The (warning) messages. */
    042    private final List<String> messages = new ArrayList<>();
    043    /** The VerificationResult cache. */
    044    private VerificationResult verificationResult;
    045
    046    /**
    047     * This method adds a (warning) message to the message pool of this PassVerifier. This method is normally only
    048     * internally used by BCEL's class file verifier "JustIce" and should not be used from the outside.
    049     *
    050     * @param message message to be appended to the message list.
    051     * @see #getMessages()
    052     */
    053    public void addMessage(final String message) {
    054        messages.add(message);
    055    }
    056
    057    /**
    058     * Verifies, not cached.
    059     *
    060     * @return The VerificationResult
    061     */
    062    public abstract VerificationResult do_verify();
    063
    064    /**
    065     * Returns the (warning) messages that this PassVerifier accumulated during its do_verify()ing work.
    066     *
    067     * @return the (warning) messages.
    068     * @see #addMessage(String)
    069     * @see #do_verify()
    070     */
    071    public String[] getMessages() {
    072        return getMessagesList().toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    073    }
    074
    075    /**
    076     * Returns the (warning) messages that this PassVerifier accumulated during its do_verify()ing work.
    077     *
    078     * @see #addMessage(String)
    079     * @see #do_verify()
    080     */
    081    public List<String> getMessagesList() {
    082        verify(); // create messages if not already done (cached!)
    083        return messages;
    084    }
    085
    086    /**
    087     * This method runs a verification pass conforming to the Java Virtual Machine Specification, 2nd edition, on a class
    088     * file. PassVerifier instances perform caching; i.e. if the verify() method once determined a VerificationResult, then
    089     * this result may be returned after every invocation of this method instead of running the verification pass anew;
    090     * likewise with the result of getMessages().
    091     *
    092     * @return a VerificationResult.
    093     * @see #getMessages()
    094     * @see #addMessage(String)
    095     */
    096    public VerificationResult verify() {
    097        if (verificationResult == null) {
    098            verificationResult = do_verify();
    099        }
    100        return verificationResult;
    101    }
    102}