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25 
26 package sun.security.jca;
27 
28 import java.lang.ref.*;
29 import java.security.*;
30 
31 /**
32  * Collection of static utility methods used by the security framework.
33  *
34  * @author  Andreas Sterbenz
35  * @since   1.5
36  */
37 public final class JCAUtil {
38 
JCAUtil()39     private JCAUtil() {
40         // no instantiation
41     }
42 
43     // size of the temporary arrays we use. Should fit into the CPU's 1st
44     // level cache and could be adjusted based on the platform
45     private static final int ARRAY_SIZE = 4096;
46 
47     /**
48      * Get the size of a temporary buffer array to use in order to be
49      * cache efficient. totalSize indicates the total amount of data to
50      * be buffered. Used by the engineUpdate(ByteBuffer) methods.
51      */
getTempArraySize(int totalSize)52     public static int getTempArraySize(int totalSize) {
53         return Math.min(ARRAY_SIZE, totalSize);
54     }
55 
56     // cached SecureRandom instance
57     private static class CachedSecureRandomHolder {
58         public static SecureRandom instance = new SecureRandom();
59     }
60 
61     private static volatile SecureRandom def = null;
62 
63     /**
64      * Get a SecureRandom instance. This method should be 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         return CachedSecureRandomHolder.instance;
71     }
72 
73     // called by sun.security.jca.Providers class when provider list is changed
clearDefSecureRandom()74     static void clearDefSecureRandom() {
75         def = null;
76     }
77 
78     /**
79      * Get the default SecureRandom instance. This method is the
80      * optimized version of "new SecureRandom()" which re-uses the default
81      * SecureRandom impl if the provider table is the same.
82      */
getDefSecureRandom()83     public static SecureRandom getDefSecureRandom() {
84         SecureRandom result = def;
85         if (result == null) {
86             synchronized (JCAUtil.class) {
87                 result = def;
88                 if (result == null) {
89                     def = result = new SecureRandom();
90                 }
91             }
92         }
93         return result;
94 
95     }
96 }
97