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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 | +} | |