MD5Calculator.java revision 0cc0544a2995c7eb54a830ae54db60af89d4073d 
1/**
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5 * use this file except in compliance with the License. You may obtain a copy of
6 * 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, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations under
14 * the License.
15 */
16
17package com.android.inputmethod.dictionarypack;
18
19import java.io.InputStream;
20import java.io.IOException;
21import java.security.MessageDigest;
22
23final class MD5Calculator {
24    private MD5Calculator() {} // This helper class is not instantiable
25
26    public static String checksum(final InputStream in) throws IOException {
27        // This code from the Android documentation for MessageDigest. Nearly verbatim.
28        MessageDigest digester;
29        try {
30            digester = MessageDigest.getInstance("MD5");
31        } catch (java.security.NoSuchAlgorithmException e) {
32            return null; // Platform does not support MD5 : can't check, so return null
33        }
34        final byte[] bytes = new byte[8192];
35        int byteCount;
36        while ((byteCount = in.read(bytes)) > 0) {
37            digester.update(bytes, 0, byteCount);
38        }
39        final byte[] digest = digester.digest();
40        final StringBuilder s = new StringBuilder();
41        for (int i = 0; i < digest.length; ++i) {
42            s.append(String.format("%1$02x", digest[i]));
43        }
44        return s.toString();
45    }
46}
47