| /* PRNG.java -- A Utility methods for default source of randomness |
| Copyright (C) 2006 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.java.security.util; |
| |
| import java.util.HashMap; |
| |
| import gnu.java.security.prng.IRandom; |
| import gnu.java.security.prng.LimitReachedException; |
| import gnu.java.security.prng.MDGenerator; |
| |
| /** |
| * A useful hash-based (SHA) pseudo-random number generator used throughout this |
| * library. |
| * |
| * @see MDGenerator |
| */ |
| public class PRNG |
| { |
| /** The underlying {@link IRandom}. */ |
| private IRandom delegate; |
| |
| /** |
| * Private constructor to enforce using the Factory method. |
| * |
| * @param delegate the undelying {@link IRandom} object used. |
| */ |
| private PRNG(IRandom delegate) |
| { |
| super(); |
| |
| this.delegate = delegate; |
| } |
| |
| public static final PRNG getInstance() |
| { |
| IRandom delegate = new MDGenerator(); |
| try |
| { |
| HashMap map = new HashMap(); |
| // initialise it with a seed |
| long t = System.currentTimeMillis(); |
| byte[] seed = new byte[] { |
| (byte)(t >>> 56), (byte)(t >>> 48), |
| (byte)(t >>> 40), (byte)(t >>> 32), |
| (byte)(t >>> 24), (byte)(t >>> 16), |
| (byte)(t >>> 8), (byte) t }; |
| map.put(MDGenerator.SEEED, seed); |
| delegate.init(map); // default is to use SHA-1 hash |
| } |
| catch (Exception x) |
| { |
| throw new ExceptionInInitializerError(x); |
| } |
| return new PRNG(delegate); |
| } |
| |
| /** |
| * Completely fills the designated <code>buffer</code> with random data |
| * generated by the underlying delegate. |
| * |
| * @param buffer the place holder of random bytes generated by the underlying |
| * delegate. On output, the contents of <code>buffer</code> are |
| * replaced with pseudo-random data, iff the <code>buffer</code> |
| * size is not zero. |
| */ |
| public void nextBytes(byte[] buffer) |
| { |
| nextBytes(buffer, 0, buffer.length); |
| } |
| |
| /** |
| * Fills the designated <code>buffer</code>, starting from byte at position |
| * <code>offset</code> with, at most, <code>length</code> bytes of random |
| * data generated by the underlying delegate. |
| * |
| * @see IRandom#nextBytes |
| */ |
| public void nextBytes(byte[] buffer, int offset, int length) |
| { |
| try |
| { |
| delegate.nextBytes(buffer, offset, length); |
| } |
| catch (LimitReachedException x) // re-initialise with a seed |
| { |
| try |
| { |
| HashMap map = new HashMap(); |
| long t = System.currentTimeMillis(); |
| byte[] seed = new byte[] { |
| (byte)(t >>> 56), (byte)(t >>> 48), |
| (byte)(t >>> 40), (byte)(t >>> 32), |
| (byte)(t >>> 24), (byte)(t >>> 16), |
| (byte)(t >>> 8), (byte) t }; |
| map.put(MDGenerator.SEEED, seed); |
| delegate.init(map); // default is to use SHA-1 hash |
| delegate.nextBytes(buffer, offset, length); |
| } |
| catch (Exception y) |
| { |
| throw new ExceptionInInitializerError(y); |
| } |
| } |
| } |
| } |