/*

 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package sun.security.jca;

import java.lang.ref.*;

import java.security.*;

/**

 * Collection of static utility methods used by the security framework.

 *

 * @author  Andreas Sterbenz

 * @since   1.5

 */

public final class JCAUtil {

    private JCAUtil() {

        // no instantiation

    }

    // lock to use for synchronization

    private static final Object LOCK = JCAUtil.class;

    // cached SecureRandom instance

    private static volatile SecureRandom secureRandom;

    // size of the temporary arrays we use. Should fit into the CPU's 1st

    // level cache and could be adjusted based on the platform

    /**

     * Get the size of a temporary buffer array to use in order to be

     * cache efficient. totalSize indicates the total amount of data to

     * be buffered. Used by the engineUpdate(ByteBuffer) methods.

     */

    public static int getTempArraySize(int totalSize) {

        return Math.min(ARRAY_SIZE, totalSize);

    }

    /**

     * Get a SecureRandom instance. This method should me used by JDK

     * internal code in favor of calling "new SecureRandom()". That needs to

     * iterate through the provider table to find the default SecureRandom

     * implementation, which is fairly inefficient.

     */

    public static SecureRandom getSecureRandom() {

        // we use double checked locking to minimize synchronization

        // works because we use a volatile reference

        SecureRandom r = secureRandom;

        if (r == null) {

            synchronized (LOCK) {

                r = secureRandom;

                if (r == null) {

                    r = new SecureRandom();

                    secureRandom = r;

                }

            }

        }

        return r;

    }

}