Source for gnu.java.security.hash.BaseHash

   1: /* BaseHash.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.hash;
  40: 
  41: /**
  42:  * A base abstract class to facilitate hash implementations.
  43:  */
  44: public abstract class BaseHash
  45:     implements IMessageDigest
  46: {
  47:   /** The canonical name prefix of the hash. */
  48:   protected String name;
  49: 
  50:   /** The hash (output) size in bytes. */
  51:   protected int hashSize;
  52: 
  53:   /** The hash (inner) block size in bytes. */
  54:   protected int blockSize;
  55: 
  56:   /** Number of bytes processed so far. */
  57:   protected long count;
  58: 
  59:   /** Temporary input buffer. */
  60:   protected byte[] buffer;
  61: 
  62:   /**
  63:    * Trivial constructor for use by concrete subclasses.
  64:    *
  65:    * @param name the canonical name prefix of this instance.
  66:    * @param hashSize the block size of the output in bytes.
  67:    * @param blockSize the block size of the internal transform.
  68:    */
  69:   protected BaseHash(String name, int hashSize, int blockSize)
  70:   {
  71:     super();
  72: 
  73:     this.name = name;
  74:     this.hashSize = hashSize;
  75:     this.blockSize = blockSize;
  76:     this.buffer = new byte[blockSize];
  77: 
  78:     resetContext();
  79:   }
  80: 
  81:   public String name()
  82:   {
  83:     return name;
  84:   }
  85: 
  86:   public int hashSize()
  87:   {
  88:     return hashSize;
  89:   }
  90: 
  91:   public int blockSize()
  92:   {
  93:     return blockSize;
  94:   }
  95: 
  96:   public void update(byte b)
  97:   {
  98:     // compute number of bytes still unhashed; ie. present in buffer
  99:     int i = (int) (count % blockSize);
 100:     count++;
 101:     buffer[i] = b;
 102:     if (i == (blockSize - 1))
 103:       transform(buffer, 0);
 104:   }
 105: 
 106:   public void update(byte[] b)
 107:   {
 108:     update(b, 0, b.length);
 109:   }
 110: 
 111:   public void update(byte[] b, int offset, int len)
 112:   {
 113:     int n = (int) (count % blockSize);
 114:     count += len;
 115:     int partLen = blockSize - n;
 116:     int i = 0;
 117: 
 118:     if (len >= partLen)
 119:       {
 120:         System.arraycopy(b, offset, buffer, n, partLen);
 121:         transform(buffer, 0);
 122:         for (i = partLen; i + blockSize - 1 < len; i += blockSize)
 123:           transform(b, offset + i);
 124: 
 125:         n = 0;
 126:       }
 127: 
 128:     if (i < len)
 129:       System.arraycopy(b, offset + i, buffer, n, len - i);
 130:   }
 131: 
 132:   public byte[] digest()
 133:   {
 134:     byte[] tail = padBuffer(); // pad remaining bytes in buffer
 135:     update(tail, 0, tail.length); // last transform of a message
 136:     byte[] result = getResult(); // make a result out of context
 137: 
 138:     reset(); // reset this instance for future re-use
 139: 
 140:     return result;
 141:   }
 142: 
 143:   public void reset()
 144:   { // reset this instance for future re-use
 145:     count = 0L;
 146:     for (int i = 0; i < blockSize;)
 147:       buffer[i++] = 0;
 148: 
 149:     resetContext();
 150:   }
 151: 
 152:   public abstract Object clone();
 153: 
 154:   public abstract boolean selfTest();
 155: 
 156:   /**
 157:    * Returns the byte array to use as padding before completing a hash
 158:    * operation.
 159:    *
 160:    * @return the bytes to pad the remaining bytes in the buffer before
 161:    *         completing a hash operation.
 162:    */
 163:   protected abstract byte[] padBuffer();
 164: 
 165:   /**
 166:    * Constructs the result from the contents of the current context.
 167:    *
 168:    * @return the output of the completed hash operation.
 169:    */
 170:   protected abstract byte[] getResult();
 171: 
 172:   /** Resets the instance for future re-use. */
 173:   protected abstract void resetContext();
 174: 
 175:   /**
 176:    * The block digest transformation per se.
 177:    *
 178:    * @param in the <i>blockSize</i> long block, as an array of bytes to digest.
 179:    * @param offset the index where the data to digest is located within the
 180:    *          input buffer.
 181:    */
 182:   protected abstract void transform(byte[] in, int offset);
 183: }