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annotate src/com/tmate/hgkit/ll/DigestHelper.java @ 9:d6d2a630f4a6

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Access to underlaying file data wrapped into own Access object, implemented with FileChannel and ByteBuffer
author Artem Tikhomirov <tikhomirov.artem@gmail.com>
date Sat, 25 Dec 2010 04:45:59 +0100
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children 571e1b2cc3f7
rev   line source
9
d6d2a630f4a6 Access to underlaying file data wrapped into own Access object, implemented with FileChannel and ByteBuffer
Artem Tikhomirov <tikhomirov.artem@gmail.com>
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1 /**
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2 * Copyright (c) 2010 Artem Tikhomirov
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3 */
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4 package com.tmate.hgkit.ll;
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5
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6 import java.io.IOException;
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7 import java.io.InputStream;
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8 import java.security.MessageDigest;
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9 import java.security.NoSuchAlgorithmException;
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10
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11 /**
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Artem Tikhomirov <tikhomirov.artem@gmail.com>
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12 *
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13 * @author artem
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14 */
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15 public class DigestHelper {
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16 private MessageDigest sha1;
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17
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18 public DigestHelper() {
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19 }
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20
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21 private MessageDigest getSHA1() {
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22 if (sha1 == null) {
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23 try {
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24 sha1 = MessageDigest.getInstance("SHA-1");
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25 } catch (NoSuchAlgorithmException ex) {
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26 // could hardly happen, JDK from Sun always has sha1.
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27 ex.printStackTrace(); // FIXME log error
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28 }
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29 }
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30 return sha1;
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31 }
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32
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33 // XXX perhaps, digest functions should throw an exception, as it's caller responsibility to deal with eof, etc
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34 public String sha1(byte[] data) {
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35 MessageDigest alg = getSHA1();
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36 byte[] digest = alg.digest(data);
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37 assert digest.length == 20;
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38 return toHexString(digest, 0, 20);
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39 }
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40
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41 public byte[] sha1(InputStream is /*ByteBuffer*/) throws IOException {
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42 MessageDigest alg = getSHA1();
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43 byte[] buf = new byte[1024];
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44 int c;
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45 while ((c = is.read(buf)) != -1) {
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46 alg.update(buf, 0, c);
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47 }
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48 byte[] digest = alg.digest();
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49 return digest;
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50 }
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51
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52 public String toHexString(byte[] data, final int offset, final int count) {
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53 char[] result = new char[count << 1];
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54 final String hexDigits = "0123456789abcdef";
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55 final int end = offset+count;
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56 for (int i = offset, j = 0; i < end; i++) {
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57 result[j++] = hexDigits.charAt((data[i] >>> 4) & 0x0F);
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58 result[j++] = hexDigits.charAt(data[i] & 0x0F);
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59 }
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60 return new String(result);
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61 }
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62 }