1 /*
2 * Copyright 1997-2006 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.security;
27
28 import java.nio.ByteBuffer;
29
30 import 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
51 public 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 }
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