1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package android.security;
18
19import java.security.NoSuchAlgorithmException;
20
21/**
22 * Base class for producing a message digest from different hash encryptions.
23 */
24public abstract class MessageDigest
25{
26    /**
27     * Returns a digest object of the specified type.
28     *
29     * @param algorithm  The type of hash function to use. Valid values are
30     *                   <em>SHA-1</em> and <em>MD5</em>.
31     * @return The respective MessageDigest object. Either a
32     *         {@link android.security.Sha1MessageDigest} or
33     *         {@link android.security.Md5MessageDigest} object.
34     * @throws NoSuchAlgorithmException If an invalid <var>algorithm</var>
35     *                                  is given.
36     */
37    public static MessageDigest getInstance(String algorithm)
38        throws NoSuchAlgorithmException
39    {
40        if (algorithm == null) {
41            return null;
42        }
43
44        if (algorithm.equals("SHA-1")) {
45            return new Sha1MessageDigest();
46        }
47        else if (algorithm.equals("MD5")) {
48            return new Md5MessageDigest();
49        }
50
51        throw new NoSuchAlgorithmException();
52    }
53
54    public abstract void update(byte[] input);
55    public abstract byte[] digest();
56
57    /**
58     * Produces a message digest for the given input.
59     *
60     * @param input  The message to encrypt.
61     * @return The digest (hash sum).
62     */
63    public abstract byte[] digest(byte[] input);
64}
65