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