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    */
BaseHash(String name, int hashSize, int blockSize)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 
name()81   public String name()
82   {
83     return name;
84   }
85 
hashSize()86   public int hashSize()
87   {
88     return hashSize;
89   }
90 
blockSize()91   public int blockSize()
92   {
93     return blockSize;
94   }
95 
update(byte b)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 
update(byte[] b)106   public void update(byte[] b)
107   {
108     update(b, 0, b.length);
109   }
110 
update(byte[] b, int offset, int len)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 
digest()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 
reset()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 
clone()152   public abstract Object clone();
153 
selfTest()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    */
padBuffer()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    */
getResult()170   protected abstract byte[] getResult();
171 
172   /** Resets the instance for future re-use. */
resetContext()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    */
transform(byte[] in, int offset)182   protected abstract void transform(byte[] in, int offset);
183 }
184