1 /* BasePRNG.java -- 2 Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc. 3 4 This file is a part of GNU Classpath. 5 6 GNU Classpath is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2 of the License, or (at 9 your option) any later version. 10 11 GNU Classpath is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GNU Classpath; if not, write to the Free Software 18 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 19 USA 20 21 Linking this library statically or dynamically with other modules is 22 making a combined work based on this library. Thus, the terms and 23 conditions of the GNU General Public License cover the whole 24 combination. 25 26 As a special exception, the copyright holders of this library give you 27 permission to link this library with independent modules to produce an 28 executable, regardless of the license terms of these independent 29 modules, and to copy and distribute the resulting executable under 30 terms of your choice, provided that you also meet, for each linked 31 independent module, the terms and conditions of the license of that 32 module. An independent module is a module which is not derived from 33 or based on this library. If you modify this library, you may extend 34 this exception to your version of the library, but you are not 35 obligated to do so. If you do not wish to do so, delete this 36 exception statement from your version. */ 37 38 39 package gnu.java.security.prng; 40 41 import java.util.Map; 42 43 /** 44 * An abstract class to facilitate implementing PRNG algorithms. 45 */ 46 public abstract class BasePRNG 47 implements IRandom 48 { 49 /** The canonical name prefix of the PRNG algorithm. */ 50 protected String name; 51 52 /** Indicate if this instance has already been initialised or not. */ 53 protected boolean initialised; 54 55 /** A temporary buffer to serve random bytes. */ 56 protected byte[] buffer; 57 58 /** The index into buffer of where the next byte will come from. */ 59 protected int ndx; 60 61 /** 62 * Trivial constructor for use by concrete subclasses. 63 * 64 * @param name the canonical name of this instance. 65 */ BasePRNG(String name)66 protected BasePRNG(String name) 67 { 68 super(); 69 70 this.name = name; 71 initialised = false; 72 buffer = new byte[0]; 73 } 74 name()75 public String name() 76 { 77 return name; 78 } 79 init(Map attributes)80 public void init(Map attributes) 81 { 82 this.setup(attributes); 83 84 ndx = 0; 85 initialised = true; 86 } 87 nextByte()88 public byte nextByte() throws IllegalStateException, LimitReachedException 89 { 90 if (! initialised) 91 throw new IllegalStateException(); 92 93 return nextByteInternal(); 94 } 95 nextBytes(byte[] out)96 public void nextBytes(byte[] out) throws IllegalStateException, 97 LimitReachedException 98 { 99 nextBytes(out, 0, out.length); 100 } 101 nextBytes(byte[] out, int offset, int length)102 public void nextBytes(byte[] out, int offset, int length) 103 throws IllegalStateException, LimitReachedException 104 { 105 if (! initialised) 106 throw new IllegalStateException("not initialized"); 107 108 if (length == 0) 109 return; 110 111 if (offset < 0 || length < 0 || offset + length > out.length) 112 throw new ArrayIndexOutOfBoundsException("offset=" + offset + " length=" 113 + length + " limit=" 114 + out.length); 115 if (ndx >= buffer.length) 116 { 117 fillBlock(); 118 ndx = 0; 119 } 120 int count = 0; 121 while (count < length) 122 { 123 int amount = Math.min(buffer.length - ndx, length - count); 124 System.arraycopy(buffer, ndx, out, offset + count, amount); 125 count += amount; 126 ndx += amount; 127 if (ndx >= buffer.length) 128 { 129 fillBlock(); 130 ndx = 0; 131 } 132 } 133 } 134 addRandomByte(byte b)135 public void addRandomByte(byte b) 136 { 137 throw new UnsupportedOperationException("random state is non-modifiable"); 138 } 139 addRandomBytes(byte[] buffer)140 public void addRandomBytes(byte[] buffer) 141 { 142 addRandomBytes(buffer, 0, buffer.length); 143 } 144 addRandomBytes(byte[] buffer, int offset, int length)145 public void addRandomBytes(byte[] buffer, int offset, int length) 146 { 147 throw new UnsupportedOperationException("random state is non-modifiable"); 148 } 149 isInitialised()150 public boolean isInitialised() 151 { 152 return initialised; 153 } 154 nextByteInternal()155 private byte nextByteInternal() throws LimitReachedException 156 { 157 if (ndx >= buffer.length) 158 { 159 this.fillBlock(); 160 ndx = 0; 161 } 162 163 return buffer[ndx++]; 164 } 165 clone()166 public Object clone() throws CloneNotSupportedException 167 { 168 BasePRNG result = (BasePRNG) super.clone(); 169 if (this.buffer != null) 170 result.buffer = (byte[]) this.buffer.clone(); 171 172 return result; 173 } 174 setup(Map attributes)175 public abstract void setup(Map attributes); 176 fillBlock()177 public abstract void fillBlock() throws LimitReachedException; 178 } 179