/*
* Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package java.util.zip;
/**
* A class that can be used to compute the Adler-32 checksum of a data
* stream. An Adler-32 checksum is almost as reliable as a CRC-32 but
* can be computed much faster.
*
* @see Checksum
* @author David Connelly
*/
public
class Adler32 implements Checksum {
private int adler = 1;
/**
* Creates a new Adler32 object.
*/
public Adler32() {
}
/**
* Updates checksum with specified byte.
*
* @param b an array of bytes
*/
public void update(int b) {
adler = update(adler, b);
}
/**
* Updates checksum with specified array of bytes.
*/
public void update(byte[] b, int off, int len) {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
adler = updateBytes(adler, b, off, len);
}
/**
* Updates checksum with specified array of bytes.
*/
public void update(byte[] b) {
adler = updateBytes(adler, b, 0, b.length);
}
/**
* Resets checksum to initial value.
*/
public void reset() {
adler = 1;
}
/**
* Returns checksum value.
*/
public long getValue() {
return (long)adler & 0xffffffffL;
}
private native static int update(int adler, int b);
private native static int updateBytes(int adler, byte[] b, int off,
int len);
}