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