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 
17 package com.android.inputmethod.dictionarypack;
18 
19 import java.io.InputStream;
20 import java.io.IOException;
21 import java.security.MessageDigest;
22 
23 public final class MD5Calculator {
MD5Calculator()24     private MD5Calculator() {} // This helper class is not instantiable
25 
checksum(final InputStream in)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