checksum.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 71 行

/*
 * @(#)Checksum.java	1.6 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program 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. 
 * 
 * This program 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 at /legal/license.txt). 
 * 
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions. 
 */

package sun.tools.javazic;

import java.util.zip.CRC32;

/**
 * Checksum provides methods for calculating a CRC32 value for a
 * transitions table.
 *
 * @since 1.4
 */
public class Checksum extends CRC32
{
    /**
     * Updates the CRC32 value from each byte of the given int
     * value. The bytes are used in the big endian order.
     * @param val the int value
     */
    public void update(int val) {
	byte[] b = new byte[4];
	b[0] = (byte)((val >>> 24) & 0xff);
	b[1] = (byte)((val >>> 16) & 0xff);
	b[2] = (byte)((val >>> 8) & 0xff);
	b[3] = (byte)(val & 0xff);
	update(b);
    }

    /**
     * Updates the CRC32 value from each byte of the given long
     * value. The bytes are used in the big endian order.
     * @param val the long value
     */
    void update(long val) {
	byte[] b = new byte[8];
	b[0] = (byte)((val >>> 56) & 0xff);
	b[1] = (byte)((val >>> 48) & 0xff);
	b[2] = (byte)((val >>> 40) & 0xff);
	b[3] = (byte)((val >>> 32) & 0xff);
	b[4] = (byte)((val >>> 24) & 0xff);
	b[5] = (byte)((val >>> 16) & 0xff);
	b[6] = (byte)((val >>> 8) & 0xff);
	b[7] = (byte)(val & 0xff);
	update(b);
    }
}