/*
* This file is part of muCommander, http://www.mucommander.com
* Copyright (C) 2002-2016 Maxence Bernard
*
* muCommander is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* muCommander 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.mucommander.commons.io.security;
import java.security.MessageDigest;
import java.util.zip.Checksum;
/**
* This class turns a <code>java.util.zip.Checksum</code> into a <code>java.security.MessageDigest</code>, allowing
* <code>Checksum</code> implementations to be used with the Java Cryptography Extension.
*
* @author Maxence Bernard
*/
public class ChecksumMessageDigest extends MessageDigest {
/** The Checksum instance that performs all of the checksumming work */
private Checksum checksum;
/**
* Creates a new <code>ChecksumMessageDigest</code> that delegates all the checksumming work to the given
* <code>Checksum</code> instance.
*
* @param checksum the Checksum responsible for calculating the checksum
* @param algorithm the name of the checksum algorithm implemented by the Checksum
*/
public ChecksumMessageDigest(Checksum checksum, String algorithm) {
super(algorithm);
this.checksum = checksum;
}
//////////////////////////////////
// MessageDigest implementation //
//////////////////////////////////
/**
* This method delegates to the underlying <code>java.util.zip.Checksum</code> instance.
*/
@Override
protected void engineReset() {
checksum.reset();
}
/**
* This method delegates to the underlying <code>java.util.zip.Checksum</code> instance.
*/
@Override
protected void engineUpdate(byte input) {
checksum.update(input);
}
/**
* This method delegates to the underlying <code>java.util.zip.Checksum</code> instance.
*/
@Override
protected void engineUpdate(byte[] input, int offset, int len) {
checksum.update(input, offset, len);
}
/**
* This method delegates to the underlying <code>java.util.zip.Checksum</code> instance.
*/
@Override
protected byte[] engineDigest() {
long crcLong = checksum.getValue();
byte[] crcBytes = new byte[4];
crcBytes[0] = (byte)((crcLong>>24) & 0xFF);
crcBytes[1] = (byte)((crcLong>>16) & 0xFF);
crcBytes[2] = (byte)((crcLong>>8) & 0xFF);
crcBytes[3] = (byte)(crcLong & 0xFF);
return crcBytes;
}
}