/*

 * Copyright 1994-1995 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.misc;

/**

 * The CRC-16 class calculates a 16 bit cyclic redundancy check of a set

 * of bytes. This error detecting code is used to determine if bit rot

 * has occured in a byte stream.

 */

public class CRC16 {

    /** value contains the currently computed CRC, set it to 0 initally */

    public int value;

    public CRC16() {

        value = 0;

    }

    /** update CRC with byte b */

    public void update(byte aByte) {

        int a, b;

        a = (int) aByte;

        for (int count = 7; count >=0; count--) {

            a = a << 1;

            b = (a >>> 8) & 1;

            if ((value & 0x8000) != 0) {

                value = ((value << 1) + b) ^ 0x1021;

            } else {

                value = (value << 1) + b;

            }

        }

        value = value & 0xffff;

        return;

    }

    /** reset CRC value to 0 */

    public void reset() {

        value = 0;

    }

}