JCAUtil.java revision 12745:f068a4ffddd2 
1/*
2 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package sun.security.jca;
27
28import java.lang.ref.*;
29
30import java.security.*;
31
32/**
33 * Collection of static utility methods used by the security framework.
34 *
35 * @author  Andreas Sterbenz
36 * @since   1.5
37 */
38public final class JCAUtil {
39
40    private JCAUtil() {
41        // no instantiation
42    }
43
44    // lock to use for synchronization
45    private static final Object LOCK = JCAUtil.class;
46
47    // cached SecureRandom instance
48    private static volatile SecureRandom secureRandom;
49
50    // size of the temporary arrays we use. Should fit into the CPU's 1st
51    // level cache and could be adjusted based on the platform
52    private static final int ARRAY_SIZE = 4096;
53
54    /**
55     * Get the size of a temporary buffer array to use in order to be
56     * cache efficient. totalSize indicates the total amount of data to
57     * be buffered. Used by the engineUpdate(ByteBuffer) methods.
58     */
59    public static int getTempArraySize(int totalSize) {
60        return Math.min(ARRAY_SIZE, totalSize);
61    }
62
63    /**
64     * Get a SecureRandom instance. This method should me used by JDK
65     * internal code in favor of calling "new SecureRandom()". That needs to
66     * iterate through the provider table to find the default SecureRandom
67     * implementation, which is fairly inefficient.
68     */
69    public static SecureRandom getSecureRandom() {
70        // we use double checked locking to minimize synchronization
71        // works because we use a volatile reference
72        SecureRandom r = secureRandom;
73        if (r == null) {
74            synchronized (LOCK) {
75                r = secureRandom;
76                if (r == null) {
77                    r = new SecureRandom();
78                    secureRandom = r;
79                }
80            }
81        }
82        return r;
83    }
84
85}
86