102 lines
1.4 KiB
Java
102 lines
1.4 KiB
Java
/* Copyright (C) 1999 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package java.util.zip;
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/**
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* @author Per Bothner
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* @date April 6, 1999.
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*/
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/*
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* Written using on-line Java Platform 1.2 API Specification, as well
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* as "The Java Class Libraries", 2nd edition (Addison-Wesley, 1998).
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* The actual Adler32 algorithm is taken from RFC 1950.
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* Status: Believed complete and correct.
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*/
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public class Adler32 implements Checksum
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{
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private static int BASE = 65521; /* largest prime smaller than 65536 */
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private int s1;
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private int s2;
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public Adler32 ()
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{
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reset();
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}
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public void reset () { s1 = 1; s2 = 0; }
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public void update (int bval)
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{
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s1 = (s1 + (bval & 0xFF)) % BASE;
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s2 = (s1 + s2) % BASE;
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}
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public void update (byte[] buffer)
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{
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update(buffer, 0, buffer.length);
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}
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public void update (byte[] buf, int off, int len)
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{
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int s1 = this.s1;
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int s2 = this.s2;
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while (len > 0)
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{
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// We can defer the modulo operation.
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int n = 4000;
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if (n > len)
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n = len;
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len -= n;
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while (--n >= 0)
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{
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s1 = s1 + (buf[off++] & 0xFF);
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s2 = s2 + s1;
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}
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s1 %= BASE;
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s2 %= BASE;
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}
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this.s1 = s1;
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this.s2 = s2;
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}
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public long getValue()
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{
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return ((long) s2 << 16) + s1;
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}
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}
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