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1 /* -*-mode:java; c-basic-offset:2; -*- */
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2 /*
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3 Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. All rights reserved.
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4
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5 Redistribution and use in source and binary forms, with or without
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6 modification, are permitted provided that the following conditions are met:
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7
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8 1. Redistributions of source code must retain the above copyright notice,
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9 this list of conditions and the following disclaimer.
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10
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11 2. Redistributions in binary form must reproduce the above copyright
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12 notice, this list of conditions and the following disclaimer in
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13 the documentation and/or other materials provided with the distribution.
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14
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15 3. The names of the authors may not be used to endorse or promote products
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16 derived from this software without specific prior written permission.
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17
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18 THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
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19 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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20 FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
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21 INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
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22 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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23 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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24 OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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25 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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26 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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27 EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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28 */
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29 /*
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30 * This program is based on zlib-1.1.3, so all credit should go authors
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31 * Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
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32 * and contributors of zlib.
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33 */
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34
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35 package com.jcraft.jzlib;
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36
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37 final class Adler32 {
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38
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39 // largest prime smaller than 65536
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40 static final private int BASE = 65521;
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41 // NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1
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42 static final private int NMAX = 5552;
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43
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44 long adler32(long adler, byte[] buf, int index, int len) {
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45 if (buf == null) { return 1L; }
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46
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47 long s1 = adler & 0xffff;
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48 long s2 = (adler >> 16) & 0xffff;
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49 int k;
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50
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51 while (len > 0) {
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52 k = len < NMAX ? len : NMAX;
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53 len -= k;
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54
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55 while (k >= 16) {
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56 s1 += buf[index++] & 0xff; s2 += s1;
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57 s1 += buf[index++] & 0xff; s2 += s1;
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58 s1 += buf[index++] & 0xff; s2 += s1;
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59 s1 += buf[index++] & 0xff; s2 += s1;
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60 s1 += buf[index++] & 0xff; s2 += s1;
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61 s1 += buf[index++] & 0xff; s2 += s1;
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62 s1 += buf[index++] & 0xff; s2 += s1;
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63 s1 += buf[index++] & 0xff; s2 += s1;
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64 s1 += buf[index++] & 0xff; s2 += s1;
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65 s1 += buf[index++] & 0xff; s2 += s1;
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66 s1 += buf[index++] & 0xff; s2 += s1;
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67 s1 += buf[index++] & 0xff; s2 += s1;
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68 s1 += buf[index++] & 0xff; s2 += s1;
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69 s1 += buf[index++] & 0xff; s2 += s1;
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70 s1 += buf[index++] & 0xff; s2 += s1;
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71 s1 += buf[index++] & 0xff; s2 += s1;
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72 k -= 16;
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73 }
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74
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75 if (k != 0) {
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76 do {
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77 s1 += buf[index++] & 0xff; s2 += s1;
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78 }
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79 while (--k != 0);
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80 }
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81
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82 s1 %= BASE;
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83 s2 %= BASE;
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84 }
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85
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86 return (s2 << 16) | s1;
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87 }
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88
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89 /*
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90 private java.util.zip.Adler32 adler=new java.util.zip.Adler32();
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91 long adler32(long value, byte[] buf, int index, int len){
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92 if(value==1) {adler.reset();}
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93 if(buf==null) {adler.reset();}
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94 else{adler.update(buf, index, len);}
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95 return adler.getValue();
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96 }
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97 */
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98 }
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