/* * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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    private final static int ARRAY_SIZE = 4096;     /**     * 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;    } }