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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 1, 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 CRC32 algorithm is taken from RFC 1952.
* Status: Believed complete and correct.
*/
public class CRC32 implements Checksum
{
int crc = 0;
static int[] crc_table = make_crc_table();
/* Make the table for a fast CRC. */
static int[] make_crc_table ()
{
int[] crc_table = new int[256];
for (int n = 0; n < 256; n++)
{
int c = n;
for (int k = 8; --k >= 0; )
{
if ((c & 1) != 0)
c = 0xedb88320 ^ (c >>> 1);
else
c = c >>> 1;
}
crc_table[n] = c;
}
return crc_table;
}
public long getValue ()
{
return (long) crc & 0xffffffffL;
}
public void reset () { crc = 0; }
public void update (int bval)
{
int c = ~crc;
c = crc_table[(c ^ bval) & 0xff] ^ (c >>> 8);
crc = ~c;
}
public void update (byte[] buf, int off, int len)
{
int c = ~crc;
while (--len >= 0)
c = crc_table[(c ^ buf[off++]) & 0xff] ^ (c >>> 8);
crc = ~c;
}
public void update (byte[] buf) { update(buf, 0, buf.length); }
}
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