android-platform-libcore/luni/src/main/java/org/apache/harmony/security/fortress/Engine.java

/*
 *  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
 *  limitations under the License.
 */

/**
* @author Boris V. Kuznetsov
* @version $Revision$
*/

package org.apache.harmony.security.fortress;

import java.security.NoSuchAlgorithmException;
import java.security.Provider;
import org.apache.harmony.security.Util;


/**
 *
 * This class implements common functionality for all engine classes
 *
 */
public class Engine {

    // Service name
    private final String serviceName;

    // for getInstance(String algorithm, Object param) optimization:
    // previous result
    private Provider.Service returnedService;

    // previous parameter
    private String lastAlgorithm;

    private int refreshNumber;

    /**
     * Provider
     */
    public Provider provider;

    /**
     * SPI instance
     */
    public Object spi;

    /**
     * Access to package visible api in java.security
     */
    public static SecurityAccess door;

    /**
     * Creates a Engine object
     *
     * @param service
     */
    public Engine(String service) {
        this.serviceName = service;
    }

    /**
     *
     * Finds the appropriate service implementation and creates instance of the
     * class that implements corresponding Service Provider Interface.
     *
     * @param algorithm
     * @param service
     * @throws NoSuchAlgorithmException
     */
    public synchronized void getInstance(String algorithm, Object param)
            throws NoSuchAlgorithmException {
        Provider.Service serv;

        if (algorithm == null) {
            throw new NoSuchAlgorithmException("Null algorithm name");
        }
        Services.refresh();
        if (returnedService != null
                && Util.equalsIgnoreCase(algorithm, lastAlgorithm)
                && refreshNumber == Services.refreshNumber) {
            serv = returnedService;
        } else {
            if (Services.isEmpty()) {
                throw notFound(serviceName, algorithm);
            }
            serv = Services.getService(new StringBuilder(128)
                    .append(serviceName).append(".").append(
                            Util.toUpperCase(algorithm)).toString());
            if (serv == null) {
                throw notFound(serviceName, algorithm);
            }
            returnedService = serv;
            lastAlgorithm = algorithm;
            refreshNumber = Services.refreshNumber;
        }
        spi = serv.newInstance(param);
        this.provider = serv.getProvider();
    }

    private NoSuchAlgorithmException notFound(String serviceName, String algorithm) throws NoSuchAlgorithmException {
        throw new NoSuchAlgorithmException(serviceName + " " + algorithm + " implementation not found");
    }

    /**
     *
     * Finds the appropriate service implementation and creates instance of the
     * class that implements corresponding Service Provider Interface.
     *
     * @param algorithm
     * @param service
     * @param provider
     * @throws NoSuchAlgorithmException
     */
    public synchronized void getInstance(String algorithm, Provider provider,
            Object param) throws NoSuchAlgorithmException {

        Provider.Service serv = null;
        if (algorithm == null) {
            throw new NoSuchAlgorithmException("algorithm == null");
        }
        serv = provider.getService(serviceName, algorithm);
        if (serv == null) {
            throw notFound(serviceName, algorithm);
        }
        spi = serv.newInstance(param);
        this.provider = provider;
    }

}