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| 1 | /* | ||
| 2 | * Copyright (c) 1994, 1995, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package sun.misc; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * The CRC-16 class calculates a 16 bit cyclic redundancy check of a set | ||
| 30 | * of bytes. This error detecting code is used to determine if bit rot | ||
| 31 | * has occured in a byte stream. | ||
| 32 | */ | ||
| 33 | |||
| 34 | public class CRC16 { | ||
| 35 | |||
| 36 | /** value contains the currently computed CRC, set it to 0 initally */ | ||
| 37 | public int value; | ||
| 38 | |||
| 39 | public CRC16() { | ||
| 40 | value = 0; | ||
| 41 | } | ||
| 42 | |||
| 43 | /** update CRC with byte b */ | ||
| 44 | public void update(byte aByte) { | ||
| 45 | int a, b; | ||
| 46 | |||
| 47 | a = (int) aByte; | ||
| 48 | for (int count = 7; count >=0; count--) { | ||
| 49 | a = a << 1; | ||
| 50 | b = (a >>> 8) & 1; | ||
| 51 | if ((value & 0x8000) != 0) { | ||
| 52 | value = ((value << 1) + b) ^ 0x1021; | ||
| 53 | } else { | ||
| 54 | value = (value << 1) + b; | ||
| 55 | } | ||
| 56 | } | ||
| 57 | value = value & 0xffff; | ||
| 58 | return; | ||
| 59 | } | ||
| 60 | |||
| 61 | /** reset CRC value to 0 */ | ||
| 62 | public void reset() { | ||
| 63 | value = 0; | ||
| 64 | } | ||
| 65 | } | ||