Source for gnu.java.security.prng.BasePRNG

   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:    */
  66:   protected BasePRNG(String name)
  67:   {
  68:     super();
  69: 
  70:     this.name = name;
  71:     initialised = false;
  72:     buffer = new byte[0];
  73:   }
  74: 
  75:   public String name()
  76:   {
  77:     return name;
  78:   }
  79: 
  80:   public void init(Map attributes)
  81:   {
  82:     this.setup(attributes);
  83: 
  84:     ndx = 0;
  85:     initialised = true;
  86:   }
  87: 
  88:   public byte nextByte() throws IllegalStateException, LimitReachedException
  89:   {
  90:     if (! initialised)
  91:       throw new IllegalStateException();
  92: 
  93:     return nextByteInternal();
  94:   }
  95: 
  96:   public void nextBytes(byte[] out) throws IllegalStateException,
  97:       LimitReachedException
  98:   {
  99:     nextBytes(out, 0, out.length);
 100:   }
 101: 
 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: 
 135:   public void addRandomByte(byte b)
 136:   {
 137:     throw new UnsupportedOperationException("random state is non-modifiable");
 138:   }
 139: 
 140:   public void addRandomBytes(byte[] buffer)
 141:   {
 142:     addRandomBytes(buffer, 0, buffer.length);
 143:   }
 144: 
 145:   public void addRandomBytes(byte[] buffer, int offset, int length)
 146:   {
 147:     throw new UnsupportedOperationException("random state is non-modifiable");
 148:   }
 149: 
 150:   public boolean isInitialised()
 151:   {
 152:     return initialised;
 153:   }
 154: 
 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: 
 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: 
 175:   public abstract void setup(Map attributes);
 176: 
 177:   public abstract void fillBlock() throws LimitReachedException;
 178: }