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 
26 package sun.security.jca;
27 
28 import java.lang.ref.*;
29 
30 import 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  */
38 public final class JCAUtil {
39 
JCAUtil()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 final static 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      */
getTempArraySize(int totalSize)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      */
getSecureRandom()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