1/*
2 * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package java.security;
27
28import java.nio.ByteBuffer;
29
30import sun.security.jca.JCAUtil;
31
32/**
33 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
34 * for the <code>MessageDigest</code> class, which provides the functionality
35 * of a message digest algorithm, such as MD5 or SHA. Message digests are
36 * secure one-way hash functions that take arbitrary-sized data and output a
37 * fixed-length hash value.
38 *
39 * <p> All the abstract methods in this class must be implemented by a
40 * cryptographic service provider who wishes to supply the implementation
41 * of a particular message digest algorithm.
42 *
43 * <p> Implementations are free to implement the Cloneable interface.
44 *
45 * @author Benjamin Renaud
46 *
47 *
48 * @see MessageDigest
49 */
50
51public abstract class MessageDigestSpi {
52
53    // for re-use in engineUpdate(ByteBuffer input)
54    private byte[] tempArray;
55
56    /**
57     * Returns the digest length in bytes.
58     *
59     * <p>This concrete method has been added to this previously-defined
60     * abstract class. (For backwards compatibility, it cannot be abstract.)
61     *
62     * <p>The default behavior is to return 0.
63     *
64     * <p>This method may be overridden by a provider to return the digest
65     * length.
66     *
67     * @return the digest length in bytes.
68     *
69     * @since 1.2
70     */
71    protected int engineGetDigestLength() {
72        return 0;
73    }
74
75    /**
76     * Updates the digest using the specified byte.
77     *
78     * @param input the byte to use for the update.
79     */
80    protected abstract void engineUpdate(byte input);
81
82    /**
83     * Updates the digest using the specified array of bytes,
84     * starting at the specified offset.
85     *
86     * @param input the array of bytes to use for the update.
87     *
88     * @param offset the offset to start from in the array of bytes.
89     *
90     * @param len the number of bytes to use, starting at
91     * <code>offset</code>.
92     */
93    protected abstract void engineUpdate(byte[] input, int offset, int len);
94
95    /**
96     * Update the digest using the specified ByteBuffer. The digest is
97     * updated using the <code>input.remaining()</code> bytes starting
98     * at <code>input.position()</code>.
99     * Upon return, the buffer's position will be equal to its limit;
100     * its limit will not have changed.
101     *
102     * @param input the ByteBuffer
103     * @since 1.5
104     */
105    protected void engineUpdate(ByteBuffer input) {
106        if (input.hasRemaining() == false) {
107            return;
108        }
109        if (input.hasArray()) {
110            byte[] b = input.array();
111            int ofs = input.arrayOffset();
112            int pos = input.position();
113            int lim = input.limit();
114            engineUpdate(b, ofs + pos, lim - pos);
115            input.position(lim);
116        } else {
117            int len = input.remaining();
118            int n = JCAUtil.getTempArraySize(len);
119            if ((tempArray == null) || (n > tempArray.length)) {
120                tempArray = new byte[n];
121            }
122            while (len > 0) {
123                int chunk = Math.min(len, tempArray.length);
124                input.get(tempArray, 0, chunk);
125                engineUpdate(tempArray, 0, chunk);
126                len -= chunk;
127            }
128        }
129    }
130
131    /**
132     * Completes the hash computation by performing final
133     * operations such as padding. Once <code>engineDigest</code> has
134     * been called, the engine should be reset (see
135     * {@link #engineReset() engineReset}).
136     * Resetting is the responsibility of the
137     * engine implementor.
138     *
139     * @return the array of bytes for the resulting hash value.
140     */
141    protected abstract byte[] engineDigest();
142
143    /**
144     * Completes the hash computation by performing final
145     * operations such as padding. Once <code>engineDigest</code> has
146     * been called, the engine should be reset (see
147     * {@link #engineReset() engineReset}).
148     * Resetting is the responsibility of the
149     * engine implementor.
150     *
151     * This method should be abstract, but we leave it concrete for
152     * binary compatibility.  Knowledgeable providers should override this
153     * method.
154     *
155     * @param buf the output buffer in which to store the digest
156     *
157     * @param offset offset to start from in the output buffer
158     *
159     * @param len number of bytes within buf allotted for the digest.
160     * Both this default implementation and the SUN provider do not
161     * return partial digests.  The presence of this parameter is solely
162     * for consistency in our API's.  If the value of this parameter is less
163     * than the actual digest length, the method will throw a DigestException.
164     * This parameter is ignored if its value is greater than or equal to
165     * the actual digest length.
166     *
167     * @return the length of the digest stored in the output buffer.
168     *
169     * @exception DigestException if an error occurs.
170     *
171     * @since 1.2
172     */
173    protected int engineDigest(byte[] buf, int offset, int len)
174                                                throws DigestException {
175
176        byte[] digest = engineDigest();
177        if (len < digest.length)
178                throw new DigestException("partial digests not returned");
179        if (buf.length - offset < digest.length)
180                throw new DigestException("insufficient space in the output "
181                                          + "buffer to store the digest");
182        System.arraycopy(digest, 0, buf, offset, digest.length);
183        return digest.length;
184    }
185
186    /**
187     * Resets the digest for further use.
188     */
189    protected abstract void engineReset();
190
191    /**
192     * Returns a clone if the implementation is cloneable.
193     *
194     * @return a clone if the implementation is cloneable.
195     *
196     * @exception CloneNotSupportedException if this is called on an
197     * implementation that does not support <code>Cloneable</code>.
198     */
199    public Object clone() throws CloneNotSupportedException {
200        if (this instanceof Cloneable) {
201            return super.clone();
202        } else {
203            throw new CloneNotSupportedException();
204        }
205    }
206}
207