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/*
* Copyright (c) 1996, 2013, 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;
import java.nio.ByteBuffer;
import sun.nio.ch.DirectBuffer;
/**
* 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.
*
* Passing a {@code null} argument to a method in this class will cause
* a {@link NullPointerException} to be thrown.
*
* @see Checksum
* @author David Connelly
*/
public
class Adler32 implements Checksum {
private int adler = 1;
/**
* Creates a new Adler32 object.
*/
public Adler32() {
}
/**
* Updates the checksum with the specified byte (the low eight
* bits of the argument b).
*
* @param b the byte to update the checksum with
*/
public void update(int b) {
adler = update(adler, b);
}
/**
* Updates the checksum with the specified array of bytes.
*
* @throws ArrayIndexOutOfBoundsException
* if {@code off} is negative, or {@code len} is negative,
* or {@code off+len} is greater than the length of the
* array {@code b}
*/
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 the checksum with the specified array of bytes.
*
* @param b the byte array to update the checksum with
*/
public void update(byte[] b) {
adler = updateBytes(adler, b, 0, b.length);
}
/**
* Updates the checksum with the bytes from the specified buffer.
*
* The checksum is updated using
* buffer.{@link java.nio.Buffer#remaining() remaining()}
* bytes starting at
* buffer.{@link java.nio.Buffer#position() position()}
* Upon return, the buffer's position will be updated to its
* limit; its limit will not have been changed.
*
* @param buffer the ByteBuffer to update the checksum with
* @since 1.8
*/
public void update(ByteBuffer buffer) {
int pos = buffer.position();
int limit = buffer.limit();
assert (pos <= limit);
int rem = limit - pos;
if (rem <= 0)
return;
if (buffer instanceof DirectBuffer) {
adler = updateByteBuffer(adler, ((DirectBuffer)buffer).address(), pos, rem);
} else if (buffer.hasArray()) {
adler = updateBytes(adler, buffer.array(), pos + buffer.arrayOffset(), rem);
} else {
byte[] b = new byte[rem];
buffer.get(b);
adler = updateBytes(adler, b, 0, b.length);
}
buffer.position(limit);
}
/**
* Resets the checksum to initial value.
*/
public void reset() {
adler = 1;
}
/**
* Returns the 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);
private native static int updateByteBuffer(int adler, long addr,
int off, int len);
}